On the refrences part on the application, do they have to be over 18 ?
yes. they ussually say that in print. if they didnt then no its not necessary.
truth is if you were the employer, would you want to hire somebody who gives you references of possibly his friends that are his same age (under 18)?
it would be smart to reference people that are in a respectable position or authority, or atleast adults.
like a school counselor, teacher, friends parent.
tell you the truth, they rarely use the references. mostly only when you might be hired for an important position. but at your age, I dont think so. you cant really get an important job at your age.
btw the only reason I assumed your under 18 is because this sounds like the first time your filling out a job application which if your over 18 you should have already have experience in it (I know..bias), and that your asking if they HAVE to be over 18. which makes me conclude you more than likely affiliate with people under 18, which in terms makes me conclude you are too. (lol just saying incase you got offended if your over 18) :D
It's not a rule that they have to be, but if your potential employer is going to take you seriously, your references really should be adults.