Science

Hey,
Maths is a bigger range and big subject which need a fresh mind. So many chapters are there. Sometimes it's difficult and sometimes it is easy.
Maths and all subject needs practice but maths need more practice.
Go through the good books and solve them. Keep the concept and formulas in a copy and learn it which will make easy to solve the problems.
I hope that you understand and will follow also.
All the best.

Just practice maths and learn formulas.

Apart from applying for the medical line through NEET or AIIMS, you can pursue B.Sc in biology, physics or chemistry, zoology, microbiology, forensic science and others. There are various other options like biotechnology, genetic engineering, and others. You can choose any of them.

It is of no problem if done before registration which is commonly done by mid-term in 11th.
It is easy to switch from science to commerce or humanities, commerce to humanities but not from humanities to commerce or science or commerce to science (It doesn't mean that it's not possible).
But these arguments were valid till last year. Earlier this year, there were some news about the same.

There is no such boundation to take maths in class 12th to pursue CA. You just need to appear for CPT for the same.

SB, Deogiri, Vivekanand, etc. are some of the best colleges.

You need to do home Science major in food and nutrition so that you can become a dietitian.

Both the courses have their own importance. It is your choice and interest that will help you to pursue your career.