Engineering

You will be eligible for both the positions after you complete your aeronautical engineering degree. IAF takes entry from AFCAT and CDS for both flying branch and technical entry, for those who are graduates.
For those who come after 12th can enter from NDA.
In AFCAT the cutoff for flying branch is

CGC Landran is quite an old name as college and had been good daily with placement as well, so better to choose CGC.

I think not but you can still do counselling so you can get an idea. I will suggest you drop and prepare if you are interested in engineering.

Hello,
These days many seats are not getting filled up in engineering colleges. Hence if you have a valid score, it's quite likely that you will get your desired branch and may be college too.

Both are good and I think you can choose according to your location and comfortability. For your reference the placement stats link is:
http://www.mnnit.ac.in/tnp/placement/placementarchive.php

You are in general category, so your chance is very low.