when you buy the csc ones do they stick even when you haven't used a ga on it yet?

Nope, unfortunately you need a GA to access any pet slots beyond your 5 original ones.

@ Darkrai well than after you use the ga they would stick right? even if you didn't use the right away? or is it that the slots only are available when you activate a ga and they will still be there to fill?

If you adopt a pet beyond 5, you're fine. But you need a GA in order to fill them, so if you were to get a GA and adopt another pet, then later abandon it, you would need a GA again to get another pet in that slot. Does that make sense?

I think so, thanks:)