simple programming

This is my first try on VEX. I have a simple programming question that need some help!
How to initiate the 15 sec auto period, which forbidden to use controller.
Should it be, when you press some button combination, then the auto mode is on. After 15 sec, it should stop and switch to control mode.
But when I’m using jostick to start and stop auto mode, is that against the rule?
Also, if I set auto mode exactly to 15 sec, there is a delay when I heard “three, two, one, go!”, thus when the 15 sec is ended, my boy maybe continue moving a little bit. Is that a big problem?
I have these stupid questions, and I really need some help.


Thanks very much!!

Toss bosses answer is very comprehensive, but I have one thing to add. Unless you have a competition switch on hand, you should not use a competition template when testing your autonomous. If you are only testing, make a separate code template that includes a task main, and put the autonomous code on there.