Application/Major Question?

Hey everyone! I just had a quick question; I’m applying to multiple UC’s (UCI, UCLA, & and
USC) next fall. I have both major requirements and pre-reqs for Sociology and Psychology. I was wondering, on the application where you can put a secondary major choice, could I get picked for that? Like, say, my first choice is psychology but it’s too full or I don’t get in; could I still get in on my secondary sociology choice? Or would I have to wait and re-apply the next semester? I’m confused on how that works! Thank you!