B.Com

Different colleges have different fee structures. Please refer to the link provided below for a list of colleges which offer B.Com in computers. You should be able to download their brochure which contains fee details of that particular college.
https://www.shiksha.com/accounting-commerce/colleges/b-com-colleges-india

No minimum percentage is required for appearing in MAT exam.

Management Aptitude Test (MAT) is a standardised test being administered by AIMA since 1988 to facilitate Business Schools (B-Schools) to screen candidates for admission to MBA and allied programmes. Govt. of India, Ministry of HRD approved MAT as a national level test in 2003. Graduates in any discipline is eligible to appear in MAT, Final year students of Graduate Courses can also apply for MAT. Majority of BSchools using MAT score has min 50% marks is graduation degree as eligibility criteria.
Refer: https://www.aima.in/testing-services/mat/mat.html

Hello Swapnil,
You have a decent CAT score. And having a B.Com degree leverages your profile as IIMs usually look for candidates having diverse educational backgrounds. You do have a chance of getting a call from IIMK.
Good luck.

Nothing is easy as you are doing graduation, so there is some level of education. But if you really wants to know then I think BCA is quite better for you to do.
All the best.

Yes. You pursue B.Com if you have 10+2 from an recognised board.