Science

It is up to your interest if you are eager to make your career in Management field than MBA is good option. If you are willing to make your career in teaching/ competitive exam/research than M.Sc Maths is good option. So, think before taking any decision.

Hi Krishna,
It is almost maths from the first semester itself, Physics and Chemistry will appear as an optional subject which is completely up to you whether you want to choose them or not, other are so many other subjects, you can choose instead of them.
Please ask if you need any other assistance.
All the best.

Yes, you are eligible for NID, if you fulfil its eligibility criteria, you just need to pass your 12th board.

General rank? General rank must be within 20 thousand, although I am not sure because it's the first time HBTU is taking admissions through JEE Mains marks.

After B.Sc Mathematics, you can pursue M.Sc in Maths, MBA in finance, MCA. You can also target various specialization courses like CA, CFP (Certified Financial Planner), CFA (Chartered Financial Analyst), CS (Company Secretary). One of the most challenging course in India in maths is Actuarial Science. Actuaries job is high paid jobs in the field of financial services.