B.Sc

For preparing for B.Sc in maths, you can take study materials from the library of DU.

Yes, Eligibility for M.A. Hindi in JNU :
Graduation with minimum 45%. Admission Process : 1. Entrance Test : Eligible candidates need to appear for the Entrance Test conducted by the University.
2. Merit Screening : Admission is based on the rank in the Entrance exam conducted by the University and Deprivation points awarded, if applicable. Separate merit lists are prepared for each category I. e. candidates belonging to SC, ST, OBC, PH categories. For more details you can visit this link : https://www.shiksha.com/humanities-social-sciences/languages/course/m-a-in-hindi-jawaharlal-nehru-university-mehrauli-delhi-120713.

Check out the below links for Colleges of B.Sc. In physics, chemistry and mathematics in India:
colleges that offer B.Sc. In Physics: https://www.shiksha.com/science/colleges/b-sc-physics-colleges-india
colleges that offer B.Sc. In Chemistry : https://www.shiksha.com/science/colleges/b-sc-chemistry-colleges-india
colleges that offer B.Sc. In Mathematics : https://www.shiksha.com/science/colleges/b-sc-mathematics-colleges-india.

As both being a graduation level course, you cannot get a guarantee of very good salary package only from these courses. But if given a choice between these two, B.Com offers better job opportunities than B.Sc. In B.Com you get knowledge of Finance, Accounting, Business Laws and Taxation which are more related to day-to-day business, so you can seek a job in small firms or you can also get certification in Tally ERP etc. And can enhance your skill in this field. While if you will go for B.Sc. There are not much job opportunities with just a graduate level degree.

No, it is not so but you should have biology then. You should have either maths or biology.

By commerce background, you can not get admission in B.Sc. Cosmetology.

For B.Sc computer science, you should have pass your 12th with maths subject with good percent, then you are eligible for the same.
Good luck.

This is a very dicy question. College level studies are very different from school studies. A lot keeps on happening in the college and at time it's very hard to resist. If you are firm and resilient enough, you can certainly manage it. Just keep a track on both the sides. Give a lot of importance to self study. Also, don't miss out the college life as it will never come back.

All groups are best! The first point is that your point of interest towards subject!