New kitten! I have a few questions regarding habits and age.

For some background information, idk the cats gender yet and she's about 2 months old? Compared to the other kittens, she bites ALOT (my hand, arm, etc.) Will she grow out of that? And is there any way to help her stop doing that? I gave her a ball toy and I'm thinking maybe she was biting due to teething?

Another question, what age should cats go to the vet? And what age can they start wearing collars?

Also, is catnip bad for cats? I know it makes them hyper and 'crazy' lol, but the current owner of the kitten says she doesn't like giving her cats catnip because it's not good for them? Is that correct?

Also, is it safe to give a little peice of turkey/cheese as a treat? (Like a cm or half a cm square), I did that all the time for my past cat and she loved it, but I want to make sure I do everything right for my new kitty.