Is it illegal to sign a contract deliberately under a made-up name? First off, the name will be completely made up, maybe using a random name generator, so this shouldn't be impersonation. What would happen if the person breaks the contract, or that everything went fine except that the company found out about the fake name afterwards?
Why does the name matter? Today, I entered into a contract to buy petrol and, later, beer and a Caesar salad. In neither case did I exchange names with the other party. If you entered into a contract under a false name with the intent to avoid your responsibilities then that would be fraud. But then, so would doing so under your real name.
The written document is given very high priority, so parties will be held to what is in the document. Both parties sign at the bottom, as a way of signalling their agreement with the terms specified in the document. If conditions are added or subtracted (by crossing out), especially with pre-printed forms, the "customer" (person who didn't write the contract) can initial such modifications, as a way of clearly signalling that they indeed agree to the deletion of such-and-such clause. Since both parties have a copy of the signed agreement, this is not strictly necessary. The potential issue would be that an unscrupulous person could cross out a clause after the contract was signed, and claimed that they aren't bound by that clause. A comparison of the two copies would then reveal that the unscrupulous person was attempting fraud. There is nothing special about handwriting in or crossing out conditions, except that it poses a potential evidentiary problem as to what exactly was agreed to, if for example one party threw away their copy and then maintained that the crossed-out clause had not been crossed out. (So, keep your copy). In case you are proposing a scenario where one party is unaware of a change, i.e. at the very last minute Smith crosses something out and signs it, and Jones did not see that happen, then both copies would be the same and Jones would be legally bound to what's in the paper. Smith should announce to Jones that a clause was being deleted. We might suppose that there are innocent reasons why Smith made changes without making an announcement to Jones, in which case the parties do not have an agreement. There may be amicable ways to deal with that situation, but push could come to shove, in which case the written form of the document is generally taken to be the most important piece of evidence (though not always the only admissible evidence, unless you're in Colorado, Florida or Wisconsin).
Disclaimer: I'm from the US and don't claim to know German or Turkish law. So let me discuss some general principles here, but details may well be different in Germany and Turkey. You're mixing together three very different things: trademark, copyright, and patent. Copyright protects the expression of an idea, in this case, the exact computer code, images, etc. If you didn't copy his code, the chance that you would coincidentally write identical code is remote. The fact that you both have a line of code that says x=x+1 wouldn't give him any grounds for a lawsuit. He'd have to show substantial portions of the code were identical. If you didn't deliberately copy his code, this isn't going to happen. Barring some extraordinary and unbelievable coincidence, you can't violate copyright accidentally. Trademark protects names and symbols used to identify a company or a product. If you decided to call your software company "Microsoft", then that other Microsoft could sue you for trademark infringement. Likewise if you copied somebody else's logo or other distinctive graphics. This is very different from copyright. It is quite possible to violate someone's trademark accidentally. Especially if he gave his company or product a rather generic name. Like if someone called his product, say, "Password Manager", someone else might make a product with the same name without ever having heard of the original. Ditto if he has some simple logo or other graphics. If you did accidentally duplicate a name or graphic elements, well, in the US a court would likely order you to change your name or graphics and that would be the end of it, unless you refused, in which case you'd end up in court. US Courts have ruled that very generic names have limited trademark protection. An example I saw recently was "Main Street Auto Repair". A court said that the owner of that name could prevent someone else from opening a shop in the same town with the same name, but he couldn't sue someone in another town who happened to use the same name. This is why, by the way, companies often use made-up words for their product names. In your case, this should be a trivial issue. If he is claiming trademark to the look of the main menu screen, just change the colors or move some buttons around. If it actually went to court, you should be able to argue that the similarity was accidental and when you were informed you promptly changed it, and that should be the end of it. Depending, I guess, on how hard-nosed the judge is, etc. Patents are different still. A patent gives the owner the exclusive right to use an invention or process for a specified period of time. It doesn't matter if you invented the same thing entirely independently. Whoever filed the patent first has exclusive rights. There have been cases where an inventor lost out to someone with a similar invention because he submitted his patent application one day later. If this other person has patents that you are infringing, you are pretty much out of luck.
In general, providing a false name or birthdate (DoB) is only actionable when there is a legal duty to provide the correct information, or when a provision of a contract to which the person agreed requires it. If the falsity is part of a common-law fraud, then it would be unlawful, and possibly criminal. In the cases listed in the question: Sign up for an online service with a false identity although the ToS requires an accurate identity: This would be a breech of contract. Whether there could be a successful suit for such a breech would depend on why the contract demanded an accurate ID, and what harm the lie did or might do. Use a false name at a restaurant or hotel, but with no intent to defraud or avoid payment. I don't think there is any duty to give an accurate name on a restaurant reservation. In some jurisdictions the law requires an accurate name be used on a hotel register, and valid ID presented. But such violations are rarely pursued, unless they are part of a fraud or some other criminal activity (theft, prostitution, or drug dealing, say). Giving a false name when opening a bank account or other financial account. In the US, and I think many other jurisdictions, the law requires accurate identification of all bank account holders, including a SSN, EIN, or TIN. It also requires a bank to make efforts to verify such IDs, and violation are prosecuted. There are legal ways to get an account under an alternate name such as a penname or DBA, but this must be disclosed to the bank and to the IRS. Other cases that occur to me: Giving a false name at a shop when not obtaining credit or avoiding payment: generally legal. Obtaining a credit card under a false name: Can be done legally if disclosed to the issuer. Giving a false name or DoB to a pharmacy for a prescription: unlawful if attempting to access the medical info of another, or rely on another person's history to get a prescription, but may be lawful if this is just an alias, such as a celebrity might use to avoid publicity. Unlawful if done to obtain a controlled substance, or if insurance fraud is involved. Putting a false name on a job resume: lawful, but if hired an I-9 form will require a valid name and SSN or TIN. Employers usually may not require that a DoB be provided. Giving false info as part of any credit application: usually considered fraud, even if there is no intent to avoid payment, as it can deceive the creditor as to the amount of risk involved; specifically criminal in some states. Giving a false name on a date: perfectly lawful, but may cause a problem if a long term relationship develops. Some states require a valid name on a marriage license.
In general, signing means you cannot deny the accuracy of the information in the future In general, there is no prohibition on knowingly stating falsehoods under the law. That is, it is not illegal to lie. Exceptions include when you are under penalty of perjury (e.g. on oath in court), when you are making certain declarations to government (e.g. your tax return), you are acting dishonestly to cause gain or harm others (e.g. fraud), etc. However, by signing the document, you may create a legal fact that is independent of the real-world facts. For example, if you sign a receipt for $1,000 then you create a legal presumption that you received $1,000 even if there was actually only $500 in the envelope. You would need some pretty spectacular evidence to overcome that presumption. Now, I don’t know what you are signing that has factual errors in it but, if they are material errors, don’t. Just don’t.
The contract remains valid. Most contracts don't need to be written at all. Even if yours did need to be written under the Statute of Frauds or some other law, you're saying that it was made in writing, even though you later tore it up. The fact that the contract is missing or destroyed doesn't change the fact that it exists and obligates the parties; it just makes it harder to prove what it said.
This is fine. You can use initials, shortened names, common nicknames (Bob/Robert), omit middle names, and so forth without causing yourself any problems. Things can get more complicated if you sign by a name that is different from names that you normally use elsewhere - such as if you are called Christopher Smith and you sign as Donald Jones, having not used that name before - but there's no fundamental difference of principle. One example case is Scott v Soans [1802] 102 ER 539, where the defendant John Soans objected to the suit being made against &quot;Jonathan otherwise John Soans&quot;. The Lord Chief Justice ruled that &quot;Jonathan otherwise John&quot; could be his name, and that if he'd signed a contract using that name then &quot;what objection could be made to it?&quot; There are several other similar cases from past centuries, some of which may no longer be reliable law since they turn on points of procedure that aren't relevant today, but the general thrust is that if you sign a contract under a certain name, then you can be sued under that name. (And you can sue other people using whatever name you like.) Mistakes in names can be corrected as part of the general process of contractual interpretation, called &quot;rectification&quot;. This more often arises when dealing with company names, say when there are a half dozen closely linked companies with related names, and the issue is which one of them is actually meant to be named; there are some recent cases of this kind, such as Liberty Mercian Ltd v Cuddy Civil Engineering Ltd [2013] EWHC 2688 (TCC). Generally speaking, as Lord Denning said in Nittan v Solent Steel [1980] EWCA Civ J1023-4, We do not allow people to take advantage of a misnomer when everyone knows what was intended. Further, the doctrine of &quot;estoppel by convention&quot; means that if you sign a contract under whatever name, then act as if you were bound by the contract, you can't then wriggle out of it on the grounds that the name is not really your own. In Scots law, which includes certain doctrines imported from Roman civil law, there is a distinction between error in persona and error in nomine. The former means that you were mistaken about who your counterparty really was (such that you wouldn't have made the contract had you known the truth) and the latter means that you had the intended person but made a mistake about their name. The law of error in Scotland is not quite the same as in England and Wales, but in this case it gets to the same basic result: if you agreed on who was to be bound, that's what matters, regardless of the names used.
The Facebook forum doesn't prevent a contract from being formed. But, for a contract to be formed there must be an affirmative agreement, not silence (at least in cases that aren't between merchants). If they later decide to work together without reaching an agreement on the details, the draft contact could be considered, but the Facebook forum for its delivery and that fact that it wasn't expressly assented to might reduce its weight as part of the evidence in an attempt to determine what the terms of their oral or implied agreement to work together involved. It would be very unusual for a broker not to get a signed agreement in writing to pay his fees, although an oral or unsigned agreement to pay a broker is not necessarily barred by a statute of frauds. A finder of fact would be quite skeptical of a broker's claim to have an agreement in those circumstances and often the professional regulatory provisions related to brokerages would require that fee agreement must be signed and in writing even if contract law does not require that this be done.