Question: If I apply to one UC and get rejected, will other UC's accept me even if I did not apply to them?

It's always nice to get good news when you don't expect it ... kind of like winning the lottery when you never even bought a ticket. ;) But, unfortunately, in this case, you can only be accepted at the UC campus(es) to which you have applied. There is a per-campus application fee ($70 per campus for domestic students; $80 for international students). So, if you want to be considered by multiple schools, you need to pay for it.