Computer Science and Engineering

BCA would be a better option if we come to getting a job. Since BCA is a technical degree and has more scope than B.Sc in computer science which only provides theoretical knowledge.

Sorry to inform you, but no. For M.Tech, either you should have a post graduation degree or undergraduate degree in a technical field that means B.Tech. You cannot go for M.Tech after B.Sc, however, some universities still offer M.Tech of 3-year duration after your B.Sc. Yes, some M.Tech courses can

Kindly visit this link:
https://www.shiksha.com/science/course/b-sc-in-physics-and-computer-science-sastra-university-thanjavur-284536

There are good chances of getting the college, check the following link to see more details:
https://www.shiksha.com/science/course/b-sc-in-physics-and-computer-science-sastra-university-thanjavur-284536

Yes, you are eligible. You need to score a minimum 50% in HSC for BCA and for MCA, you should opt for maths in BCA.
All the best.

You can do BCA where you'll learn some coding languages but you can't do B.Tech in CS.

Just decide on the basis of your interest. Then do search on the available options on the chosen subject as a career field. But yes since you've got 80 in maths I guess you have a descent control over maths and you should go for maths, it has a good scope.

If you are from commerce background, you have a huge opportunity the following are list of course, you can opt for
law with Honours:
B.Com
BBA
c. A
icwa
CS
cma
B.Sc computer Science, computer technology, software system
B.Sc psychology
B.A English literature
Integrated BBA-MBA form IIM, Indore or other uni

I'll prefer you to opt for the IPEC as this college is the best college in all the other college that you have mentioned in the list above as this college in all the terms whether it is infra, faculty and placements.