If you're only 16, why are you worrying about applying to colleges? I waited until two months ago to apply to a college and I got my acceptance letter yesterday.
LFC must live in the UK, because in the UK you apply to and go to college at 16.
In the UK you do your GCSEs between the ages of 14 and 16, college from 16 onwards (you can stay for as long as you wish by doing other subjects at AS/A2 Level) and then once you have enough UCAS points you can apply to University.
Indeed, A-Dust is correct. But by 'stay as long as you want' he meant stay until you pass something lol.
Not necessarily, although I can not see why you would want to spend a long time in college. Unless however you return as a senior student to improve your career prospects, or just want to learn something.