Is it legal for two individuals in California, United States to place a bet between themselves? Alice wants to make a bet with Bob (e.g., betting 100 USD that tomorrow there will be no snow falling in a given location, or that some new phone to be announced tomorrow will cost less than 1k USD). Bob agrees to the bet. Is that legal, and is the bet legally enforceable (i.e., Bob must pay Alice if he loses)?
No California has no laws on social gambling so it is treated identically to commercial gambling. Since betting on outcomes other than sports betting is illegal in California, such a bet would be illegal. While it’s unlikely to be prosecuted, as a contract it would be void its illegality and thus unenforceable.
I do not know the particular legal environment in France, but in general the shop is private property and the owner decides who may enter and who may not. You have no right as such to enter somebody else's property against their will. Doing so would at least be classified as trespassing, possibly more serious considering you mention using force to enter the premise.
This doesn't sound like fraud (against you, at least), but it does sound like an unfair or deceptive trade practice, which is outlawed by Section 5 of the Federal Trade Commission Act and perhaps the Pennsylvania Unfair Trade Practices and Consumer Protection Law, both of which prohibit unfair and deceptive trade practices. I don't know about Pennsylvania, but the FTC has on many occasions taken action against companies for engaging in just this kind of behavior. To find out whether you would be able to take action against the other company, you'd want to find a good competition lawyer in Pennsylvania. For some more basic background on the FTC's rules, check out this primer.
If the employee has the choice - bonus and membership, or no bonus - then I expect the offer to be legal. Since it is a real bonus and part of your salary you will have to pay income tax on it. What might be illegal, but not your concern, is if your company tells investors how well the company is doing, and how well the membership scheme is doing, when in reality 80% of members are employees paying effectively nothing.
It is not prohibited in California under EDC §49011, though your local board could make it prohibited. In-person solicitation of goods or money during school hours is prohibited in NY state, under Regents Rule 19.6, but recruiting children during school hours is allowed.
There is no federal prohibition against sexual discrimination in public accomodations. Colorado has an applicable state law, which covers "any place of business engaged in any sales to the public", where "It is a discriminatory practice and unlawful ...to refuse, withhold from, or deny to an individual or a group, because of ...sexual orientation...the full and equal enjoyment of the goods...". No provision exempts lemonade stands. Churches etc. are specifically exempted: "'Place of public accommodation' shall not include a church, synagogue, mosque, or other place that is principally used for religious purposes". Sex discrimination is allowed "if such restriction has a bona fide relationship to the goods, services, facilities, privileges, advantages, or accommodations of such place of public accommodation", an argument that can't reasonably be made in the described case. It is also not obvious that running a lemonade stand is a business (the courts will not admit unsubstantiated Wiki assertions as evidence). It would be relevant to wonder what constitutes a "business" under Colorado law. E.g. is a business license required? In Colorado (US) law, it has not been definitively decided whether there can be a religious exception to the anti-discrimination law. Masterpiece Cakeshop was decided without answering that (the state showed clear religious intolerance in its handling of the case). We do not know how a similar case will be decided: Arlene's Flowers was handed back to the state court with the instruction "do it again" (with nothing more than a mention of Masterpiece Cakeshop). The court cannot establish certain beliefs and practices as "valid religions" (Establishment Clause); the proxy expression that is used is "deeply held belief", which includes atheism. The relationship of the issue to the First Amendment is uncertain.
It depends on the rules of the particular betting market and the laws under which it operates. Assuming that the bet itself is legal, it is not uncommon that participants in the contest are not allowed to bet, not because they distort the market, but because they can influence the outcome. Consider if instead of betting to win, Mr Trump bet on himself to lose and then do something which would reduce his chances (hard to imaging what he could do that he hasn't done but anyway).
In the US, "insider trading" includes both legal and illegal versions. When a corporate employee buys or sells shares of their company, they are insiders and they are trading (there is a requirement to report to the government). The illegal version involves breach of fiduciary duty or confidence. The relevant section of the federal regulations is 17 CFR 240.10b on "Manipulative and Deceptive Devices and Contrivances", and you will note that the section does not rely on the term "insider" in the law part, instead it directly characterizes what acts are illegal. Thus it would not matter, from a legal perspective, if someone considers you an insider. It is illegal to trade in securities using a “manipulative, deceptive, or other fraudulent device or contrivance”. This relates to what is commonly known as insider trading via rule 240.10b5-1, by defining as manipulative and deceptive trading on the basis of material nonpublic information about that security or issuer, in breach of a duty of trust or confidence that is owed directly, indirectly, or derivatively, to the issuer of that security or the shareholders of that issuer, or to any other person who is the source of the material nonpublic information (emphasis added to focus on the core requirements). Whether or not you have a "duty of trust or confidence" is determined by common law standards, that is, it depends on how courts have ruled on similar matters. For instance if the CEO of Apple tells you "Our computers explode and it's gonna be on the news tonight, the stock is gonna tank, but it would be illegal for you to act on that information", then it would be illegal, because you are aware that the CEO has a duty to not use that information (thus you "inherit" the duty). This also holds if he doesn't tell you that acting on the information, since it is expected that you know that the CEO of Apple could not legally act on that information (even if in fact you are unaware of the law -- ignorance of the law doesn't get you anywhere good). However, if you are unaware and could not know that the person making the factual disclosure is divulging information that he has a duty to shut up about, then you might not get prosecuted.