Defer and Apply Elsewhere?

Was recently just accepted to my second favorite school, but rejected from my first favorite.

Is it possible that I could request to defer enrollment for a year on the premise that, though I love the (second favorite) school, I would like to spend part of my gap year applying to another school?

Would Ivy level schools revoke admissions if someone hypothetically deferred admissions to school A, and then applied to school B without school A knowing, and then got accepted and attended school B? Would school A and/or school B rescind the kid?

Each place sets its own policy about this. You need to ask them.

I think that you will get better advice if you tell us what schools you were accepted to, and what school you were not accepted to. Knowing what you want to study and whether the school that you were accepted to is affordable without loans would also be useful.

I agree with @happymomof1 that this is likely to vary from school to school.