Dear kishan,

It you got failed in the 12th standard and passed again after 2 years then the JEE mains allow to you because it doesn't matter whether you failed several times or not ,  JEE mains not focus on how much have you failed it only focus on passing the board with at least of aggregate of 60 percentage in any Board.

so yes he is eligible to apply jee mains 2021.

Hello !!

Yes..he is eligible and can appear for jee mains 2020 .If a candidate have passed 12th class and equivalent exam in 2018 and 2019(but not before 2018) are eligible to apply for this exam.Just go through the link provided below for more details about eligibility criteria of mains 2020:

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

Hope that helped you!!

Good luck achiever and do prepare well !!