What and all I should learn to to develop a game

Answer 1

kWS

Answer 2

Do you mean what languges should you learn to develop a game?

Generally speaking Java, C++ and C#. But to be honest with you, if you're just starting, learn any language you want! This is because any good progrommer knows multiple langues and it's not that hard to transition between languges.

But... If you want to learn Unreal Engine I suggest C++ and if you want to learn Unity use C#.

Hope it helps :D