If an object did not have inertia, and a centripetal force acts on it, how fast would it go and what radius would it turn in? Also, could the object turn in the beginning/middle of a turn without slowing down? Also, can something without inertia turn while in the middle of changing direction and do the same thing many times?

Depends on how you're using the term inertia. An object at rest cannot feel a centripetal force. An object can turn without slowing down.