M.Tech Mechanics

GATE score required for IISC-Bangalore is more than 750. For safer side, your score should be 800 above to get good branch.

Basically, you need to write entrance exam of any private college. So, do well there and get admission without GATE.

Evening/distance/online/part time engineering courses are not valid any more as per the latest supreme court verdict, hence would recommend you to join regular B.Tech course for better career prospects-
http://www.tribuneindia.com/news/nation/no-technical-education-through-correspondence-says-supreme-court/491819.html.

If you are definitely going to Aeronautical in M.Tech then you should take B.Tech aeronautical because having same branch in both undergraduation and post graduation makes you skilled in the particular field.

Sorry to say that the minimum criteria for admission in M.Tech is 60% marks in Jamia Mila Islamia. Still, you can opt for other colleges where the minimum criteria for admission is 50% marks.