While I disagree with the teenagers’ ability to find my banking passwords regardless of where I hide them, for example because I can make a copy of them that has been altered with a password I can calculate in my head and that takes the location of the password on the table into account in the calculation, the rest is true.
I remember having seen things I really wouldn’t want to see even as adult when I was browsing Internet for stuff that wasn’t supposed to be available. Shady websites can be shady in so many ways! It is true that making an age verification system for a basic porn site will probably direct the youth to other sites with content you wouldn’t see on PornTube. I hope my children won’t ever watch porn, but if they ever do, I hope it’s from a source that doesn’t allow the worst things to be shown. For example PornHub does remove the worst stuff and is quite commonly used. If that one cannot be accessed, then probably something else will. And it’s likely to be worse. Though, PornHub has a lot of really bad abusive things as well. Checked it out now and one of the first videos it showed was something that looked like the woman is really unhappy, even distressed, about the situation she’s being filmed in :(
What you’re looking for is PostmarketOS. On their website you can also see what tablet devices it runs on more or less perfectly and on which ones some of the features are missing.
I think their website answers all of your questions.