Edward Furlong was 14 when Terminator 2: Judgement Day in 1991. And it is R-Rated. My question is: Was Edward allowed to watch this movie with a bunch of his under-age friends. Or do they make an exception for the actor? Actually this applies to all other R-Rated movies with child stars in them.
First, the Motion Picture Association of America's (MPAA) film-rating system is voluntary and not enforced by law. Still, most theaters in the United States enforce the ratings and don't let children under 17 into R-rated films without a parent or legal guardian. So it's really up to a child actor's parents whether or not they're allowed to see an R-rated movie that they appear in.
One notable rumor (confirmed in an interview) where a child actor was not allowed to see an R-rated movie in which they appeared was Olivia Hussey who appeared in the 1968 production of Romeo and Juliet at the age of 16. The film got an R-rating for nudity. It's ironic that Hussey would not have been allowed to see the film in U.S. theaters because she was the one who appeared nude.