B.A

Yes, you can appear for CAT entrance exam. If you would be able to crack CAT exam, then you can go for MBA. For MBA, you need to be graduate from a recognized university.

Hi,
Rachna Sansad School of Design provides the following course in interior designing:
B.Sc. In Interior Design - Y.C.M.O.U. (Nashik) Degree
School of Interior Design
Three Years
Eligibility: 12th (H .S. C)
Intake: 60 Students
Prof. Prasad Badle, Principal
All the best.

I think, you must go with philosophy. Since, you are from DU, I think you already have good command over English. For literature, you can read books of Shakespeare for English and Premchands for Hindi.

Curriculum for both is similar, the only difference is that BHM is more of the management of hotel industry and other one is more into tourism service industry.

Below mentioned are the best colleges:
1. St. Stephen's College.
2. Delhi School of Economics (DSE).
3. Shri Ram College of Commerce (SRCC).
4. Lady Shri Ram College for Women (LSR).
5. Hindu College.
6. Hans Raj College.
7. Ramjas College.
8. Miranda House.
You can check the below mentioned link:
https://www.shiksha.com/humanities-social-sciences/economics/colleges/b-a-colleges-india

Civil services examination is very competitive therefore, MA can be a good standing option.