While it is too early to talk about 2022, and failing in 2020 and 2021, to give you a peak into the eligibility criteria, for being eligible for BITSAT 2022, you should have completed your 12th in 2021 or 2022. So if you have failed in 2020, you need to reappear for the entire subjects and secure a minimum aggregate of 75% in Physics, Chemistry and Mathematics. Let's say hypothetically if you fail in 2020 and pass in 2021, you are eligible for 2022 BITSAT.