University of Mumbai [MU]

Hello Devprakash,
This is something which depends on your interest. If you are interested in more technical knowledge in your field, you can opt for M.Tech or MS. Otherwise, you can opt for MBA as well. MB can open other career opportunities for you. So, you need to analyze your decision and take appropriate decision.

Educational:
1. For Bachelor program in psychology, you need to pass class 12th.
2. For Post graduate courses in psychology, you need to have Bachelor's degree in psychology.
3. For Ph.D/ M.Phil, you need to have PG or Diploma in psychology.
Hence, it would be difficult to get admission in PG as you do not have the graduation in the same field.

No, you cannot change your specialization after completing 2nd year of B.Tech.

Yes, as per my knowledge you can change your college during the 3 year or 5 year course. If you are changing the college within the same university, then there is no problem. But, if you have to change the university, then you might face some trouble.
As per one of the common rule of Universities in India, if you are migrating from university to university between your course, then you will have go through an evaluation process. As per this process, the new university will assess your papers, which you have given in your last university.

No, you cannot chance once you have been admitted into a certain course. You have to continue with your course else discontinue the same and rejoin with your preferred course.