Science

Yes, after completing 12th class studies, you can take admission in BBA. There are too many career options available for 12th science (biology) students. You can check some of the most popular career options here: http://articles.abilogic.com/196120/topmost-career-options-12th-science.html
I hope it will help you to choose the right direction for your career. For colleges go through this link:
https://www.shiksha.com/bba/colleges/bba-colleges-delhi-ncr

Here is the link to help you-
https://www.shiksha.com/university/patna-university/patna-university-blet-exam-question-papers

The refund process varies from college to college. In most of the colleges, fees is non-refundable. You need to check with the college about its refund policy after admission.

No, you cannot apply for that. You should complete your B.Sc degree first in order to pursue M.Sc degree.

To get an answer to your question, I would advise you to please get in touch with the college specifically. Here are the contact details for you, in this link-
http://www.ccsuniversity.ac.in/web/Contact-us.htm
Or write at registrar@ccsuniversity.ac.in

Minimum passing marks required in 12th are 60%, if you want B.A. (Hons) in English at St. Xavier's College. Mandatory subject is English. Also, check this link-
https://www.shiksha.com/humanities-social-sciences/languages/course/b-a-hons-in-english-st-xavier-s-college-kolkata-park-street-35664

You need to appear for the exam- Panjab University Common Entrance Test PG or PU-CET (PG) to get admission in M.Sc. This exam is the gateway to get this course. The exam shall be conducted on 8th and 9th June, 2019. For detailed information, you may click this link-
https://www.shiksha.com/university/panjab-university/pu-cet-pg-exam?course=1039

Below is the eligibility criteria to get admission in B.Sc, at Mount Carmel College:
1. You need to clear class 12 or equivalent exam from a recognized board.
2. You need to study the language (second language) studied at the last qualifying examination.
https://www.shiksha.com/college/mount-carmel-college-palace-road-bangalore-24896/admission#admission

No, there is no entrance exam for admission in the mentioned course. Admission is based on graduation percentage. Candidates who have studied B.Sc./ B.A.(Hons) in Mathematics/ B.Sc.(Hons) in any subject wit mathematics as elective subject / B.Sc. general with mathematics.