I think it's been scientifically proven
People can change .. but generally, they don't permanently.
No but its rare. Mental equivalent of homeostasis
Because he is a leopard and he was born with those spots. The same can be said of all cats, and dogs and horses, etc.
it depends on the person
I think the potential to change is within nearly everyone, and that a leopard can change his spots if he's willing to put the effort and time into doing so.