B.Tech

As SRM university main campus is widely preferred, it is better to take civil engineering course there. You can have better infrastructure and placements too.
So, it is worthy to take civil at SRM University, if you can pay the fees.

It's a very good combination. At present, most recruitment of healthcare MBAs are happening in IT/Consulting companies and they usually prefer someone with computer science background. However, you have to be careful about selection of institute. Some healthcare management institute mostly promotes

Hi,
No, you can't change your college after 6-7 months of regular study.
There is no college that will allow you take admission and continue your studies from where you left them.
I hope you understand my point.

When it comes between VIT and SRM, I would opt for VIT University only.
VIT:
Good placements, better education and exposure. Campuses like Vellore and Chennai are better for all the courses.
Fee structure is better, but it increases with your rank. For the ranks 25000 and above, the fees will be INR

You told your rank, but did tell about your exam.
So, I take this rank of yours in JEE Mains. So, with such nice rank you can get NIT or any reputed college, which take admission through JEE Mains. So, appear in JEE Main counselling, which I think has started, so hurry.

Yes, you can get a seat at SRM University at any of the campuses except main campus. You can get the campuses like Delhi NCR, Ramapuram campus etc.
So, try to get a good course in the counselling.

If you get the main campus of SRM University (KTR campus), then you may not choose PES and Sathyabama University as SRM main campus will be better. If you get the other campuses, then go for PES or Satyabhama University.

Of course in India, the best college for dual degree are NITs.
Some of the NITs offers dual degree course in B.Tech biotech.
Other private colleges for dual degree courses are meaningless.

Take GMAT, and purse Masters abroad.
Work there and earn.