Hi Gourab,

As per the eligibility criteria of JEE Main 2021, a student who have passed class 12 or any other qualifying the exam in 2019 or 2020. Now, as you have mentioned you have passed 12th this year i.e. in 2020 so yes, you can write JEE Main 2021 (April) and you can also prepare for 2022 attempt. Also you can go for JEE Advanced, if you qualify JEE Main.

Refer here for more info - https://engineering.careers360.com/articles/jee-main-eligibility-criteria#JEE-Main-2021-Eligibility-Criteria

To know your other best admission possibilities of Institutes & branches in JOSSA & State counseling as per your percentile, You can use JEE Main College Predictor tool given below

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

Feel free to ask doubts in the Comment Section.

I hope this information helps you.

Good Luck!