Is it advisable to remove a screw after the bone has fully healed?

Only if painful. If the screw is irritating, then it can be removed, otherwise, avoid the surgery.
If loose or. Oyherwise bothering you it is fine to remove a screw.
Only if problematic. The screw is not needed after the bone heals. It should only be removed if it is creating discomfort by backing out and is palpable on the skin. If it is in contact inside of a joint and you are experiencing pain with motion.