Hello,

There is no number of limit to appear for NEET UG. So if you haven't qualified in NEET UG  2021 or haven't scored decent rank then you can a year drop and prepare for NEET UG 2022 and appear. It does not matter if you have registered for NEET UG 2021. You can appear for NEET any number of times. As of now there is no upper age limit to appear for NEET UG until supreme court passes its judgement regarding the upper age limit for NEET UG.