Hey there

JEE mains is a national level exam for admissions into nits, iiits, gftis etc. The eligibility criteria for enrolling in the exam is you should have passed or in 12th. Not more than 3 attempts are given the first attempt is the year of your board then consecutive two years. For admissions into nits etc the 75% or top 20 percentile matters.

Check about eligibility for JEE mains

https://www.google.com/url?sa=t&source=web&rct=j&url=https://engineering.careers360.com/articles/jee-main-eligibility-criteria/amp&ved=2ahUKEwjH3ta13tfkAhUSbisKHaaKCuwQFjAAegQIAxAE&usg=AOvVaw0Ddf__yVIUe0laa-JjEit-&ampcf=1 good luck