See most of the chapters (90% of the syllabus) is linked with each other i.e., you will need in most cases your knowledge of 11th and 12th both for solving problems.

In Physics, Modern Physics is the chapter which have no links with most of the other chapters. So you can study that.

In chemistry, some how you will need the knowledge of other chapters in order to interpret. Although if you go for the Physical Chemistry portions then you can manage as a standalone subject.

In Mathematics most of the things can be learnt provided you must have a good basic knowledge till 10th atleast such as Trigonometry, Geometry etc.

**As you can see, most of the chapters are linked, so studying them separately with quite a good amount of time investment is expected for success.

For more information regarding the JEE MAINS 2022 syllabus, consider the link below:

https://engineering.careers360.com/articles/jee-main-syllabus-weightage

I hope this helps. Wish you a great eve!