Hey there

I can see that you are in a lot of pressure. First you need to take a deep breath and be calm. Wonders can be achieved in  3 months. The syllabus for jee main is your 11th and 12th together. Focusing on 12 the syllabus more is  logical right now for you. Cover up the 12th syllabus first as it will also help you in your boards examination.

Get ready as you don't have a single minute to waste.

For chemistry 12th class syllabus only NCERT is enough. I repeat only NCERT.

If you have gone through each and every question of the book and you actually get it and not just cram it up, you don't need anything else.

for 11th class chemistry you only need a few chapters of ncert, not the whole book and you will be able to get decent marks in jee.

For maths(both 11th and 12th)  try to take out ncert first. As you are left with less time I will not refer RD Sharma but if somehow you manage to get some time do try to solve it too otherwise just take previous year question paper and try to solve them and practice them.

For physics you actually need to make effort as 11th class physics is a bit tougher than 12th class. If you are done with 12th class physics without giving it a second thought go for 11th class physics first and then any other subjects

I wish you all the best!

Hello Aspirant,
these book are the best for any student to score good marks in jee mains as well as jee advanced 2021 for preparing in 3 months.
physics:
H.c.verma for theroy part of physics and cengage for objective part of physics.

Mathematics:
R.d.sharma for theroy part of mathematics and cengage for objective part of mathematics.

Chemistry:
NCERT books are the best for the theroy part of chemistry. Himanshu pandey for orgaric chemistry objective part and o.p tandon for the remaining objective part of chemistry.

If you can read all these books perfectly then you can have the ability to crack the jee mains as well as jee advanced exams.I Hope it will helps you.

Thank you.