Hey!

Accoriding to the JEE Mains eligibility criteria, you need to clear 10+2 or equivalent in 2018 or 2019 to appear for JEE Mains. Candiddates appearing for 12th boards in 2020 can also apply. There is no age limit as such.

Candidates may attempt JEE Mains both the time in a year, for 3 consecutive years.

For appearing in JEE Advance, you must have cleared JEE Mains and must be below 25 years of age.

JEE Advanced can be attempted a maximum of two times in two consecutive years.

Hope this answer helps!