Hey Kartik.

To become a doctor you need to take Medical Stream in Class 12th. After that you would be required to complete an MBBS degree. Entrances in India for MBBS in any college throughout is NEET. Other than that there are only 2 other entrances in India for AIIMs college and JIPMER. 

After that if you wish to specialise in certain branch you can pursue MD/ MS. For that also there are 3 entrances- NEET PG, AIIMS PG, JIPMER PG. If you want to specialise further depending upon your branch there is an MCH course for a few branches too.

Best of lucl!