PES University

You can refer the previous years of COMEDK. But, PESSAT may be a little tuff compared to COMEDK.

If you are getting PES-Bangalore, go for it. The above 4 institutes are good. But if we arrange them in preference order so it is like PES-Bangalore, SRM-Chennai and Amity-Noida, and VIT-Bhopal. Choose wisely. See their rankings, review, placements, faculty, etc.
Good luck.

The branch changing not only depends on grades. You need to be in the top 20% of your batch. Also, upgradation of branch happens, if the seats are available in that branch (in which you want to go). As far as I have known, upgrading your branch from BioTech to Mechanical is difficult.

Yes, she can get a seat in civil or maybe biotech. You can wait for the second round as you may get a better branch.

With this rank you will be able to get biotech and civil for sure. You also stand a close chance for mechanical. You can wait for the second round and try your luck.

In Tamil Nadu it almost nearly 10 lakhs to complete your UG.

Yes, you can get CSE with this rank in PES. Since, the number of seats have increased you may get CSE in the first rank.

To get admission in B.Des you need to appear for the exam conducted by the college PESSAT. After you get your rank you can sit for the counselling. As for this year the exams are over and the results are out. You can visit the college website for more info.
www.pes.edu

Sorry to say but with a 10k rank it is difficult to get a seat in PES. Also there are no scholarships at the time of admission. You can get a scholarship after you get your CGPA in the first semester and onwards.