Hi

hope you doing well

Yes, you will still be eligible to write both JEE Mains and JEE Advanced , as long as you meet the eligibility criteria.

Eligibility for jee mains:

To appear for JEE Mains, you need to have passed your 12th board exams (or equivalent) with Physics, Mathematics, and one additional subject (like Chemistry, Biology, or a vocational subject).

Failing in one subject in 11th grade won't directly affect your eligibility for JEE Mains as long as you pass 12th grade with the required subjects.

Eligibility for jee advanced:

For JEE Advanced, you must be among the top performers in JEE Mains and pass 12th board exams.

Even if you clear the failed subject in a supplementary or improvement exam, you’ll be considered eligible for JEE Advanced, provided you pass all subjects required for your board’s 12th qualification in the same academic year.

hope you get it and find it useful

Best Wishes.