Hello aspirant,

You can give your jee main exam of 2021  .But it is important to see that you also apply for jee advanced after you qualify in jee mains . Scoring high in jee mains doesn't let you into nits etc. It is only a path to qualify to write jee advanced to get in to IIT 's.But unlike other Colleges you can't get into second year and you need to start from the first year .

All the best.