B.Com

Yes, you can go in the teaching line after completing your B.Com. You need to have a B.Ed degree to appear for TGT exam.

If you are going for MBA in future then it is better to go for BBA instead of B.Com.

No, it is not compulsory to take an entrance exam.

Yes, you need maths if you want to pursue B.Com (Hons) from Manipal University, Jaipur.

It is going to be very difficult for you to get an admission in IIM Bangalore, without some good Work Ex and CAT marks, as IIMB gives graduation marks very high weightage in comparison to other colleges. And, after getting in you will actually need work extra hard to justify the lower marks in graduation that you have (but, with hardwork that is possible.)
Anyway, you can also look at IIM C and L which don't give as much emphasis to past acads.
Good luck.

Since you have not mentioned your university, it is quite difficult to say. But, in general, it sure does seem possible. A lot depends on the marks of people around you (as IIM Bangalore grades your marks relative to others and then gives your application some points). Anyway, it does seem possible, just score as high as possible in your CAT.

Hello Shrutilekha, The admissions for various undergraduate courses in colleges affiliated to Pune university will begin only after results of 12th are declared by Maharashtra board. Many colleges have online process only for ease of students. You must make use of it.

Yes, you can purse a specialisation in marketing with B.Com as long as you have the interest.
All the best.

A candidate is eligible to appear if one holds atleast 50 percent marks or equivalent CGPA (Bachelors degree).