Hi Nikhil,

It is great to see that you are interested in theoretical Physically and am here to give you for the same.

Assuming that you are pressing your Higher Secondary education it lower, you basically have to courses of action from here:

Either you can study hard for JEE and secure a seat in the B.Tech. Engineering Physics stream of a reputed institute like IIT-B, then do your M.Tech. course and then go for a pH.D.

Or else, you could do a B.Sc. in Physics, following which you have to do an M.Sc. and then go for a Ph.D.

The entrance exam for Ph.D. courses in India is GATE and that for Android is GRE. Once you have warned the right to call yourself "Doctor", any institute will be happy to have you on board.

As far as success is concerned, that completely depends on your hardworking and dedication level to the task at hand.