Diploma

Not sure. Because pursuing technical Diploma courses through the Correspondence/ Distance modes are not valid in India a per AICTE guidelines. Hence avoid to do these.

It is good to do MA in mass communication. It also gives you a master degree and you are able to study more about mass communication.

The fee can be varying according to colleges. The fee structure of NID for B. Des Interior design is given below.
1. B. Des total course fee : Rs 1207800 (Without hostel)
2. B.Sc. Interior design fee per semester : Rs 98000 (LPU Jalandhar)
3. Diploma Interior design fee per semester : Rs 15000-50000 per year.

Yes, you can do if you have completed 3 years Diploma in Interior Design or Architectural Assistant ship or Civil engineering. After 10th or [ (2 years/ 1 year after 10+2)] or equivalent.