Colleges in Kolkata

You should choose Arts if you want pursue B.A.

Yes, you are eligible to take admission in this college because according to the eligibility criteria you require 45% in 12th.

For MA in English, first you have to BA in English. For good colleges for Bachelors and Masters you can go for DU. For Masters in English a candidate should have completed BA or any graduate course after 10+2 with any field.

For BA, you can pursue anything in class 12th. There is no subject eligibility criteria for BA. But, I would suggest pursuing science, as it could later help you to pursue many other courses. You can take English and Hindi Literature in class 12th if you want. That could help but not much.

Yes, you are eligible for CAT Exam for admission in IIM-A and IIM Calcutta. To know more visit: https://www.shiksha.com/mba/exams/cat.

Maths in 12th is compulsory along with a total passing percentage of 50%+. This the the least eligibility for BCA.

To know about the study centre, please visit the link given:
http://www.wbnsou.ac.in/study_centres/List_of_Study_Centres_for_BDP-PG-BLIS_for_Admission.shtml#sc_bdp_pg_blis

I think there is a slight confusion here. IISWBM & IIM are two seperate entities. For IISWBM, you need to get 60 percentile in order to secure your place plus your GD-PI performance matters.

I am afraid that is possible all the time.
I think the MSW courses are not available in Bengali.
You can look for the books in Bengali in the college.