Is it legal to make two competing brands of the same product without making the public aware of the common source? Suppose I create rocket boots and brand them as "Super Jumpers". After a couple months of selling them, I stealthily create a new brand of rocket boots called "Mega Fliers". I do not publicly reveal them as created by the same person or corporation, and perhaps I even market them with improvements I intentionally left out of the original boots. Would this alone be illegal, or only under certain conditions? For example, if I had a monopoly on rocket boots, if I was inflating prices, or if using other consumer manipulation to make them purchase more of both.
You mean like Unilever, and countless others do? Yes. Many, many companies control a stable of brands, often of competing products. This is particularly prevalent in grocery lines (cleaning, food, beauty products) and motor vehicles (there are dozens of brands of motor vehicle but only a handful of automotive companies). Clearly, these products have different features (improvements) – you are entitled to segment your market anyway you like. If they are actually produced by the same company, keeping that secret would be virtually impossible. If they were separate companies (even with licencing agreements etc.), well, they are not the same company even if they have common ownership. As for having a monopoly: if you hold a patent you are allowed to have a monopoly, if you don't, expect to see knock-off rocket boots on the shelf in a week.
Does a situation like this constitute breach of contract and/or a violation of advertising laws? No. There is not enough information that would lead to a finding of either. It is unclear how customers would be allegedly affected (if at all) by the release of a product at a different store, let alone where the goods or services at issue are digital and require no physical presence at a venue or premise. Except for very specific factual circumstances, a change of sales venue would hardly be cognizable as deceptive or unfair practice. Also, prior to purchasing or reserving a game, there is no contract between the public and the developer/supplier. Potential customers typically are not entitled to a specific performance by the developer. Even if [Phoenix Point] supporters' decision were provably based on the prospect of release at Steam, your description nowhere reflects that there was a mutually conscious exchange (or promise of an exchange) of considerations involving the parties' support of a game and the counterparty's release of the game at a specific venue. Absent that meeting of the minds, either party's reliance or expectation on the other is irrelevant. Generally speaking, the sole cruciality of either party's motives does not create legal obligations.
Under US law: It depends, but it is likely legal. Trademark is designed to prevent confusion in consumers, to avoid someone's good work and reputation from being taken advantage of by another, and/or damaged by another's poor work/service. The game's name and character names are (generally) not trademarked, nor are they copyrightable. Even if they were, there is nominative fair use to consider as a defense. There are still some legal issues that might occur (e.g. this does not apply to the novel's name; using the game's logo on cover art might constitute trademark violation if it was so positioned as to be associating a relationship with the game publisher, descriptions of the game's content, especially story content, is a bit hazy), but not with using the game name or character names.
Copyrights protect the mark as is, and derivatives of it, but does not protect the brand from look a likes or from new trademarks that would be confusing. Consider the Pepsi logo: I could easily draw a circle half red and half blue with a white line straight across, vertically, or diagonally. In fact: © 2018 A. K. all rights reserved. There it is my new logo for my cola company called Hep-C (I'm raising awareness). Under copyright law Pepsi could not come after me because the logo is my own creation. I could even call it Pepsi and it would not be a copyright violation as you cannot copyright words. However, Pepsi has better lawyers than that and with my trademark so similar to theirs and the name sounding so similar (and my new name being potentially disparaging to Pepsi) it would likely confuse consumers between what was Pepsi and what was Hep-C thus under trademark law it would be disallowed for commerce. Now you would have common law trademark protection by virtue of using your mark in commerce, but it would only be for the states in which you used it. Additionally a lack of a registered trademark would disallow you from seeking statutory damages under 15 U.S.C. § 1117.
In your example is the spare part the subject of a design patent? I assume it is not. When you combine the spare part to create a “different product” does the finished product resemble the drawings in the design patent? If, in its intended use, the final thing is close enough to the design patent to fall within its scope then you might by indirectly infringing by inducing people to infringe. The scope of a design patent is very difficult to determine reliably. This has nothing to do with how you got the components of your product, just how the completed thing looks. Copyright does not cover products (unless it is a model of a building or a statue or mold for a statue).
20th Century Fox have a trademark on "Simpsons." They have trademarks on "Bart Simpson", on "D'oh", on "Duff Beer". I would assume that they take their trademarks seriously. What you can't do is to use someone else's trademark to make people believe your commercial product is related to theirs. It's quite reasonable to assume that someone seeing your book in a store would think it is written by the makers of The Simpsons show and therefore buy it. Even if you say that isn't your intention, it is what would happen. I'd try coming up with some different titles, maybe "How to write animated TV shows" with "Example: The Simpsons" (well, you are the writer so you should come up with something better), and take them to a lawyer. And then contact the makers of the show (again asking the lawyer for advice how to do this) because even if your lawyer says the title is fine, that doesn't mean you can't be sued.
This is unlikely to be a problem. There are many companies that have already registered software-related trademarks prominently involving an X or the name Xcom. That Twitter has changed to X branding does not substantially change this general situation. With trademarks, the general question is whether similar branding causes confusion. It is unlikely that someone would confuse the X display server / X.Org project / X.Org Foundation with the social media service now being branded as X or x.com. Of course, anyone can sue anyone, the real question is whether that's possible successfully. Here, I have my doubts that x.com could successfully demonstrate confusion in its favour. It is worth noting that the X.Org Foundation does not seem to hold any relevant trademark registrations at all. This is not unusual for Open Source software projects and doesn't mean that X.Org has no rights, but does make a defense a bit more difficult. However, there also doesn't seem to be a relevant registration by the ex-Twitter company or by the X Corp. The x.org domain name is unlikely to be threatened. If the x.org domain name was being used in bad faith it could maybe be seized, but the X.Org Foundation has a pretty strong claim on this name. For historical context, both x.com and x.org were among the six single-letter .org/.net/.com domain names when such registrations were stopped in 1993. But while x.com has been pretty much dormant since that company was renamed to PayPal, x.org has (I think) always been associated with the display server software, and has been used continuously by the X.Org Foundation since its establishment in 2004.
Neither law has precedence - manufacturers have to obey both. The FD&amp;C says that they don't need to list ingredients which are trade secrets; the CFR says they must. If they list the trade secrets they do not break either law. If they don't, they break the CFR. Conclusion: they must list the trade secret ingredients. If the FD&amp;C said it was forbidden to list trade secret ingredients, but the CFR required it, manufacturers would still have to obey both laws - which would mean they couldn't sell anything where one of the ingredients was a trade secret.