B.Sc

In order to seek admission in B.Sc in psychology, you have to complete 10+2 stage from a recognised board. Unfortunately, Diploma is not directly equivalent to 10+2. You will have to check with each university where ever you apply for B.Sc in psychology whether they accept Diploma in engineering as equivalent to 10+2 or not.

Vellore is one of the leading universities. You may get a better placement from this college.

Institute of Hotel Management, run by ministry of Tourism are good places. Known as IHM, these places offer many specialisations as well. Most of the universities have their hotel management institutions like Kurukshetra University has or even Amity University, Noida has. It depends on which region are you asking about.

Selection of course completely depends on you. Decide what interests you the most and then go through the details of the course. You can find everything online.
All the best.

First, you need to clear the subject in which you have a compartment then think about any UG course.

IISC doesn't offer B.Sc. It only offers Ph.D, integrated M.Tech and integrated Ph.D programmes.