Shreedhar, there is no upper age limit for NEET. The Supreme Court has placed a Stay on the upper age limit order for NEET. If you belong to ST Category, you should complete your 12th with a minimum aggregate of 40% in Physics, Chemistry and Biology. If you fulfil this eligibility criteria, you are eligible for appearing in NEET. And yes, if you can score a minimum score of 500 , you can get a MBBS seat. It is possible to become a Doctor.