B.Tech Aerospace Engineering

You are eligible, but as your cut-off is low, you cannot get top colleges. Try the below link to find the suitable colleges:
http://cutoff.annauniversitycounselling.com
Good luck.

General Category:
749 (Opening)
2036 (Closing rank)
OBC Category:
383 (Opening)
1037 (Closing rank)
SC Category:
157 (Opening)
425 (Closing rank)
ST Category:
173 (Opening)
231 (Closing rank)

It depends on the students performance but the placement is good in aerospace engineering.

Yes, you can get lateral entry as a DSY (direct second year) for BE in aerospace.

B.Tech and M.Tech from the same branch is the best option because in that, you have a vast experience in that field that would be beneficial in every form.

There is no question that aerospace engineering is good, and also packages of this branch is unbeatable, but there seats are limited as well as jobs are limited there, but the mechanical branch is the evergreen branch.

You should prepare for JEE Mains and Advance. You have to clear this exam. This exam is organized in all over the India to take admission in IITs, NITs, IISAT and other government engineering colleges. You should prepare for IISER Pune and IISST Thiruvananthapuram. These are the best colleges in India for aerospace engineering.