Just want some questions answered.

Can't seem to get any answers from the court and child support services. If anyone can please answer my questions, I'd be so thankful.
Does child support stop at 18? What if they go on to college?

If I get behind on child support during the year and when its my year to claim the kids, I know that I don't claim my kids. What if I catch up with my payments before the end of the year, Can I still claim the kids?

What if one of my kids wants to live with me for a year? Do I still pay child support to his mom that year?

When does a child start making their own decision on visitation? According the divorce decree I have them for a month every summer and every other holidays. This summer my ex said my teenage daughter is old enough to make her own decision to come or not. I just don't understand the system at all?