Electronics

You can opt for MS programme and look up in which field you are good.

Universities those offer other degrees along with engineering named their engineering degree as BE (Bachelor of Engineering) and Institute constituted for only Engineering studies named their degree as B.Tech (Bachelor of Technology). BE is Bachelor of Engineering whereas B Tech is Bachelor of Technology.
Both are same.

As it is an NIT, getting admission would be quite difficult there as you don't have any quota except the home state one. I can not say for sure that you will be able to get admission into ECE. So, I would recommend that you apply for other branches or look into other colleges. You can also apply for IIIT Una which has the same faculty and campus as NIT Hamirpur and has the CSE, ECE and IT branches. With your rank, there is a chance that you can get admission into IT or ECE in IIIT Una.

That's true, it all depends on your interest but one should always check the growth with respect to the subject. There has been saturation with respect to CSE but still some exceptions are there. You can opt for electrical or mechanical too which is still growing rapidly.

This year, SRM has changed its admissions criteria, they have fixed the fee for a range of 10,000 I.e. each set of 10,000 will have the same fee e.g. 1-10,000 has a different fee, next 10,001-20,000 have different fee structure and the fees increases after each set of 10,000. So, you can get computer science in the main campus, but it will be very costly.

Definitely yes it is a very good university.

According to me, ECE branch is better than mechanical. With ECE, you can go for both private and government sectors
and there are also more chances of getting placement in ECE branch as compared to mechanical.

Yes, students with Diploma certificate recognised by the State Technical Body are deemed eligible.

Both are good, It totally depends upon how much knowledge you gain.