Yes you can definitely apply for both 10+2 merit basis and JEE mains basis for JIIT Noida. According to the latest admission brochure of JIIT for the year 2021,  if a candidate is applying under JEE (Main) 2021 category and also wants to apply under NRI Category/ 10+2 marks based admission, the candidate must apply separately by paying the required application fee.

For 10+2 marks based admissions, candidates should have a minimum of 60% marks (55% for SC/ST) in aggregate in 10+2 or its equivalent examination.

If admission is based on the marks merit, the result must be submitted before the preparation of merit as per admission calendar 2021.

Best of luck!!