I am thinking of taking drop and giving jee mains again and I can achieve good rank, but I have a doubt that the 75% is applicable for 2021 also or not?

Dear student,

If you think you can do it, then definitely you can get success. Because for getting success you first have to believe that you can do it. And if you are willing to take a drop then you must take a drop and if you have caliber then definitely you can secure a very good rank.

Now till last year, there was a class 12th eligibility criteria that - students must have to pass their class 12 with 75% aggregate marks and it was mandatory till 2019.
But for this year (due to this covid-19) the class 12th passing eligibility criteria has been given a relaxation, and now you just have to pass your class 12th exam and there is no such criteria this year that you must secure 75% in a class 12th board exams.

But there is no official release that this criteria will be continued in 2021. It may be possible that this relaxation will be scrapped in future, so it will create a problematic situation if you have not 75% in aggregate. So for putting yourself on a safe and secure more more than 75% in class 12th board exams and after that there will be no headache that whether you have to secure 75% or not in class 12th. If the situation gets normal of the covid-19 then it might be possible that this class 12th passing relaxation will be scrapped next year.
But still you must not wait for offical notification, if you don't have 75% in class 12th then you better secure 75% in class 12th first.