B.Sc Maths

Check this link:-https://www.shiksha.com/university/dr-harisingh-gour-vishwavidyalaya/dhsgsu-uget-exam

The course offered by BIT Mesra is M.Sc (Math and Computing) not B.Sc (Math and Computing), however, exit option is available after 3 years. Admission for M.Sc course is based on marks obtained by the candidates in Class 12th / equivalent qualifying examination. Hostel accommodation is available for all students in general. We will be happy to hear from you in case of any more queries. Please visit BIT Mesra website www.bitmesra.ac.in for more details.

You can take statistics with B.Sc. hons Maths.stats is related to Maths and scope is too high.

You have a very Brilliant rank so you have a greater chance of getting the main campus

The best college for B.Sc Maths (H) is Deen Dayal College and there are no other college better than this in Delhi for B.Sc Maths (H).

Yes, you can join navy by taking Combined Defence Service, this itself provides all the training of arms and ammunition to the cadets. Enroll yourself in CDS and work hard.

No, it is not necessary while pursuing B.Sc (hons-maths) to have Physics.
You can pursue B.Sc (hons-maths) even without studying Physics.

for this you have to go to the respective website and apply for the college and also look out for the cutoff