dear sahil Ahmad

you can give appear for JEE MAINS exam till the age of 24 according to 2019 eligibility criteria.

for reserved categories age limit is 29. but number of attempts are limited to 3.

and you can give JEE ADVANCE every time you clear JEE MAINS.

for more information refer to the following link:

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

GOOD LUCK!