Hi

I am extremely sorry to tell you dear but you are not eligible for JEE mains 2021.

This is because,

One is eligible for giving JEE mains only for 3 consecutive years from the year of passing class 12th board examination so if you have passed in 2018 , you were eligible for JEE mains 2018 ,2019 and 2020 only

For example,

Eligibility criteria says that to be eligible  for JEE mains 2021 for BE or Btech you just must be either appearing for 12th board exam in 2021 or should have passed it in 2020 or 2019 with Physics,  mathematics and anyone of Chemistry or Biology or Biotechnology or Technical Vocational Subject.

For detailed information go through

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

Thankyou