Hello dear student

• Candidates must have passed their XII or equivalent exam in 2019, 2020 or appearing in 2021 can sit for JEE Main 2021 .
• Candidates who passed class XII or QE in 2018 or before as well as those who will appear in such examination in 2022 or later are not eligible to appear in JEE Main 2021

• Candidates get six attempts – two attempts , January and April, each year for three consecutive years for JEE Main while for JEE Advanced only two attempts are allowed as per rules.
• Even after qualifying JEE Main with top ranks in their 3rd attempts students are not permitted to appear in JEE Advanced.

Please visit the link for more information.

https://learn.careers360.com/engineering/jee-main/

Hope that's helpful

Best of luck