B.Tech

You can go through this link http://www.collegesintamilnadu.com/TNEA-2015/Srinivasa-Institute-of-Engineering-and-Technology-Chennai/Cut-off-mark/Rank/220.

Hello Thushar,
For doing Masters or MS abroad, one needs to have done graduation in similar branch so that basic understanding is available in the student. However, I would advise you to approach an agency that is dealing with sending students abroad for MS to know different nuances.

It is good to see your dream of becoming an aeronautical engineer. I am attaching a link that will give you all the required information about top colleges in Andhra Pradesh. https://www.shiksha.com/b-tech/ranking/top-aeronautical-engineering-colleges-in-andhra-pradesh/49-2-100-0-0.

Admission Procedure and Eligibility in Triguna Sen School of Technology
B.Tech :
Candidate must have passed 10+2 or equivalent with Physics, Chemistry, and Math from recognized board.
75% admission is done through JEE Main conducted by CBS E. And, remaining 25% through School Entrance Exam.

BCA or B.Tech, choose any one of them, if you want to step-in the world of computer education. Your +2 marks is low, so there is probability that you may not get good colleges for B.Tech. But, on this +2 marks, if you are getting a good reputed BCA college, then don't show any hesitation to take admission for BCA. Now, who says BCA is bad? It is a very good and career growing degree. If you join MCA after your BCA, in any of the NIT through NIMCET, then there is no better option than this.

Of course, you can take admission in civil engineering. But, it is tough to get government college on that score of JEE. You may go for admission in private colleges for civil engineering.

Yes, for that engineering institutions conduct a separate test for Diploma students. After clearing it, one can have lateral entry to engineering colleges.