Dear aspirant hope you are doing well...

yes you are eligible for the jee mains exam. You can appear in jee mains exam in 3 consecutive year including 12th appearing session. Now As you said once youhave failed in class 12th exam it's mean you have only two chances to crack jee mains. That's means you have only 2 consecutive year for crack jee mains including this year.

For more details, you can read the article..

application form dates.. Eligibility criteria, addmission, detailed syllabus  , exam pattern, pervious years cut off, top colleges and their fee structure in details. You can read the article..

.. Link is given below..

https://engineering.careers360.com/exams/jee-main/amp

Hope it's helpful

Thank you.