Boarding schools and SYA

Considering SYA for junior year, and coming from a member school.

Does anyone know how financial aid works if the student receives FA at their school? Do they apply for school aid again or through SYA?

Do schools generally have a cap on how many students can go, or how many they let apply? And who makes the decision to accept, SYA or does the school influence this?

Just wondering if FA students do less well in acceptance to SYA or if the school can hold them back for institutional need, etc.

Any responses or experiences you wish to share are welcome!