alt Hacker NewsYou need a passport associated with it, you don't necessarily need to be an adult I think. Or the parent's is fine. Either way you will have to try quite hard to get a FB account not associated with a real life identity. And then they'd shadowban you.
In the UK, pay-as-you-go SIMs are widely available. Not sure how much information you need to give to activate+use one these days, though.