Do you still have to be 18?

R rated movies require those who are 17 and under be accompanied by a parent/guardian over 21 years old. Additionally, the theatre may deny children 6 and under admission to R rated movies even with a 21 + adult.

Yes

Yes, however that is very loosely enforced. 17 and under requires an adult.

Any thing rated R you have to be 17 or older or with a guardian over 18

No

? 18 for what