Hello,
As you have plenty of time for JEE 2021 I would suggest you to first go for the NCERT Book for Physics to clear the basic concepts. Once you are clear with your basics, you can go for practicing questions from previous years question papers. You will get an idea about the types of questions. For physics, HC Verma is the very basic book needed for clearing the higher concepts. If you want to score good marks, then you must have practiced from HC Verma. Then only you will be able to solve questions from JEE advanced.
Here's a list of best books for jee mains
https://www.google.com/url?sa=t&source=web&rct=j&url=https://engineering.careers360.com/articles/best-books-for-jee-main/amp&ved=2ahUKEwjts4XDn9bpAhX87nMBHdACAxwQFjAAegQIARAB&usg=AOvVaw1wil8ti_ze9MSV-Wo_mLsd&ampcf=1

Also, you can go for the JEE mains course by Careers360 which will provide 24x7 faculty support, doubt clearing, frequent mock tests and previous year question papers solutions.
Here's the link for that
https://www.google.com/url?sa=t&source=web&rct=j&url=https://learn.careers360.com/&ved=2ahUKEwibtce-oNbpAhUj4nMBHRAjAX0QFjAAegQIAxAB&usg=AOvVaw1ygKzacnBaQOPGaLiWbSgF
Hope it helps

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