Hi

NTA had released jee mains 2021 application form on 16th December 2020 in online mode at official page of jee main i. e jeemain. nta . nic . in . and that time one had the opportunity to apply for February session and rest of the three sessions as well

And yes,
Application Window will be reopened again for each of the sessions separately but dates for the same has been not released yet

The application Window will be reopened just after the declaration of February session results and that time you can apply for March session and the rest of the sessions as well, similarly application window will get reopened after march session results and that time one can apply for April session and May session also . Finally application window will get opened for the last time after April session results and that time one can apply for May session.

Now that,
limited time is left for jee mains 2021 , so you should be focusing on your preparation, go through chapters first , major focus should be on grasping concepts , practising questions and then revising them, go through previous year question , and mock test papers as it will let you know your preparation level and and weak areas so that you can work on them and perform well in your examination.

For details about JEE main you can check out our page the link is provided below:-
https://engineering.careers360.com/exams/jee-main

If you have any other doubt then you can always reach us to clear them :) we are always available to help you out and guide you

Thankyou