Dear Akhinandan, NEET is the entrance examination for admission to Medical, Dental, Ayusj and Veterimary courses. So if you want to study MBBS either in India or abroad, NEET is mandatory. And once you appear for MBBS and secure a seat, it is a 5 and 1/2 year course. This includes 1 year mandatory internship. Now regarding the fees, the seat in a Government Medical College is less than a lakh annually. But a seat in a Private Medical College costs you anywhere from 8 lakhs to 25 lakhs and above.
ELIGIBILITY FOR NEET:

• Indian Nationals, NRIs, PIOs, OCIs, and Foreign Nationals
• No upper age limit as of now. The Candidate should be at least 17 years by December 31st of 2020
• You should have completed your 10+2 with Physics, Chemistry and Biology as your Core Subjects.
• 50% Aggregate in Physics, Chemistry and Biology for General Category, 45% for PWD and 40% for OBC,SC,ST Candidates.
• NIOS and Private Candidates are also eligible

And for studying MD, you need to appear for NEET PG currently. But within the next 3 years your final year marks will be considered for securing admission. So we do not yet have an idea of how that would change.