Are there movies you have to be 21 to see?

Answer 1

Not in the United States, no. I don't know about other countries. In the States, the most restrictive rating is NC-17 (no one who is 17 or under is admitted, not even if they have a parent or guardian with them). If you're 17 or under, you can see an R-rated movie if somebody over 17 buys the ticket and sees the movie with you. But with NC-17 movies, absolutely no one 17 or younger is admitted.