Quote: "They can't refuse to sell you two tickets no matter who they're for."
Where did you hear that? It's simply not true.
I used to work in a movie theatre, and we would always refuse to sell tickets to underaged kids. Some kids thought they were smart by using their interac cards to buy the tickets from the automated machines, but as the tickets were different colours, we weren't easily fooled.
Quote: "In the US, isn't it illegal to date someone under the age of 18 when you are a legal adult?"
Highly doubt it. Illegal to sleep with someone under aged 18, yes (even if you're 18 and she's 17). But to date? Not as far as I know. In Canada it's something like 14, which is waaay too low IMHO.