Career

Army recruits through entrance tests and a string of physical tests and exercises. They have a very stringent eligibility criteria like height, weight, eyesight etc. If you qualify all of the above, then , yes, you can may become an army officer

There is a world of options after 12th with commerce. The decision rests in the domain or field you want to study or work in

If you have PCM in +2 then you are eligible to become Commercial Pilot. You can join any of DGCA approved flying club for training yo becomr pilot. You can also appear for NDA entrance exam and opt for Indian Air Force to become Pilot in IAF.

The placements in MIT for mechanical engineering is quite decent. Big companies come but they come a little late, in the 8th semester mostly. Most people say that placements in mechanical engineering in MIT are not so great. I won't deny that but it's not bad either. On an average you get an annual package of 5-6 lakhs.

You may not able to do regular MSc and PhD while on job. However you may able to complete your education by distance learning while on job.