You're half right about this, and 100% wrong in all your remaining comments.
In the US, even if the actor is 18 or over, it's still kiddie porn if he or she is portraying a fictional character who is under 18. In such cases, the actor could be 24 years old and it's still kiddie porn. So it need not be a violation of the rights of a minor. We just punish it because we don't like the effect the portrayal has on people watching it. We don't want people to see it.
Entirely incorrect. Under Miller v. California, the state may prohibit "obscenities" meeting a definition set forth by the SCOTUS in that case. It's a vague standard, but the federal government and all 50 states have obscenities laws. Traditionally they've only enforced them against the most extreme pornography.
https://en.wikipedia.org/wiki/Miller_v._California
For example, the pornographer Paul Little aka "Max Hardcore" spent 2 and 1/2 years in federal prison in Texas on obscenities charges, from 2009-2012. He was also charged at various times with kiddie porn but it was the obscenities charges that landed him in jail.
Apparently the state lost a major obscenities case about 5 years back and both the feds and states haven't been enforcing these laws since. They remain on the books, however. And since they're structured to meet the Miller standard, they are constitutional unless Miller is ever overturned.
Do you even check sources before opining on legal issues? I'll just link wiki for you on this one.
https://en.wikipedia.org/wiki/Fighting_words
You're wrong again. Liability for false advertising isn't based on harm caused. States have false advertising statutes to punish false advertising whether or not there is harm or a complaining citizen. But the standards are quite permissive. They are allowed to engage in mere "puffery" which is something like better than lying but worse than telling the truth. It has to be an out and out factual lie to be subject to liability.
It's a criminal action typically pursued by the state's AG against the advertiser. Private individuals have no right to pursue the theory, only the state. Individuals can sue advertisers if they suffered financial harm, but then it would be fraud, not false advertising. The state can pursue it just for being false. It's not often pursued, but I believe all 50 states have such laws. Example:
https://www.shouselaw.com/false-advertising
Four strikes and you're out.