No
Yes as far as i know you can, You parents may not agree but i think at the age of 18 you can make up your own mind on it.
40
That depends on your perspective. When you're a teen, if your parents are around that age, 40 seems incredibly old. When you're thirty, 40 seems like middle-age, the end of your young adult life, and...
I believe today's 40-year-olds are part of "Generation Y."
Middle aged, male and human.