When I studied in FIITJEE, these are the topics my teachers told I would have to focus on properly:

• In physical chemistry, try to learn concepts and formulas of electrochemistry, thermodynamics , solid, liquid and gaseous states.
• In inorganic chemistry, try to learn block chemistry .
• In organic chemistry, try to learn as many reactions as you can, but first learn biomolecules and polymers .

If you want to know all the topics required, then I would advice you to see this answer of mine:

https://www.careers360.com/question-what-are-most-important-topics-in-jee-mains-2017-that-can-assure-cutoff-marks-within-the-10-days

Hope this helps you and all the very best!