Hey !

You can apply in those colleges when their admissions are on. Some of the universities asks for your previous semester's or year's grade cards or mark sheets. and then, later you got to submit your 12th mark sheet once it is out.

SAT,IELTS and all can be attempted any number of times . It's preferable that you start off with SAT exams in your 11th grade itself and then keep on attempting till you achieve your target score. Few books for SAT that can kelp you includes Barrons and Princeton.

All the best !