MBA Entrance Exam

Yes, you can prepare from home and can appear for CAT. However, it would be quite difficult for you to get admission in IIMs until you are born genius.

It is not possible for you to get admission for CSE in any of the NITs. You can only go for other government colleges or private institutes if you want to pursue CSE.
If you want to pursue other branches then you can get admission in any of the NITs.

Hello,
When it comes to the MBA entrance exams, all of them include maths. The concepts of maths asked in such exams are of school-level, so only practice is required in acing this section. To get admission in any good college, one has to compulsorily give one or the other entrance exam, score high in it, and clear the interview rounds (if shortlisted).

Hello,
Preparing for an MBA entrance exam usually takes 3-6 months of dedicated preparation:
https://www.shiksha.com/mba/articles/20-mba-entrance-exams-you-can-take-this-year-blogId-11473.

It depends on you, if you want you can take one year's gap for CAT preparation. It's not compulsory.

It depends on you, if you want you can take one year's gap for CAT preparation. It's not compulsory.

If you want, you can join any coaching institute. If you don't want to join any institute then you can only study through online courses.

Start reading newspaper for Verbal, it's helpful for vocabulary and for Quantitative practice daily. If you want, you can join any coaching institute. If you don't want to join any institute then you can only study through online courses.

Maths is very important for Quantitative so if your maths is not good then firstly focus on that it's important start from basic maths like percentage, odd number, prime number, even number, graph, pie chart and many more after that for verbal start reading newspaper specially the editors page it's helpful for vocabulary.