[Humble]

Please,
1.What is correct here
He needn’t do that, …? – Yes, he … .The key in my book gives – must he?- Yes, he must. Is it the only possible variant?
2. Is it possible to use have got to in the interrogative and negative?
Have you got to do it right now?
You haven’t got to do it right now.
3. Any difference here?
a)You’ve got to hide your love away.
b)You have to hide your love away
c)You must hide your love away.
Tnx.