Dear Uttara gupta,

Yes he can apply for IMU CET in 2021 . But as per the policy he should have passed the exams till that time. So the board results mostly get out in May then he will be eligible for the exam. As per the eligibility criteria he should have qualified 12th standard (or equivalent) examination with Physics, Chemistry and Mathematics from any recognized central or state board and should be be minimum 17 years and maximum 25 years old as on August 1, 2021.

There are more criterias which you can see from below link.

https://engineering.careers360.com/articles/imu-cet

Hope it helps.