B.Sc Maths

You need to do Diploma through distance because our education system doesn't allow to do 2 regular courses simultaneously.
Check out the distance course availability in this college.

You have various options to opt for:
1. Actuarial Sciences
2. MBA
3. GMAT
4. GRE
5. Banking and finance
6. Data Analyst

If you really are into mathematics and want to study further then only you should for M.Sc. And if believe in entering the real world and want to look for a job and earn by yourself then I would say banking and finance is better.

The fees structure for B.Sc maths varies from university to university and from college to college. For exmaple the fees for B.Sc mathematics in different colleges of Delhi University in North Campus varies from 13000-20000 whereas the fees for some colleges in South Campus or off campus colleges is around 7000.

No. The answer is obviously a no. You'll have to start from the very starting.

Did you mean you want to pursue Maths (Hons) in post graduation? If yes, then you will have to appear for entrance test of every government institute you want to take admission in. If you want to go in IIT you will have to appear for IIT JAM. If you want to go fir research in your subject along with post graduation you can apply for TIFR. For private colleges, there arena't any entrance tests.

Yes, of course, you can get admission in maths hons in Delhi University at least and other state Universities too. There may a little deduction in your percentage though while calculating for best 4.

If you are really determined or really want to take admission in renowned government institute like Delhi University, you can drop a year. But that according to me will be wastage of time. You can take admission in state University. They will surely provide you admission. State Universities like MDU or KU will definitely provide you admission. In case you go for dropping a year, you can also prepare for IIT-JEE.

You can go for M.Sc. in any of the above subjects. For that, you will have to take entrance test. Institutions like IITs provide admissions on the basis of IIT JAM result. Option for civil services is always there. You can take SSC CGL exams. If you have good teaching skills, you can apply for coaching institutes like ALLEN or Akash.