GATE

You should get at least 60+ marks to get admission in the college you want.

Yes,
There is a seat reservation for lower castes in GATE exam also. There are some seat reserved for OBC/SC/ST in GATE exam also. You can check all these details also by going GATE official website. Thanks dear. I hope my answer will satisfy you. All the best dear.

Apart from GATE, some universities have their own college exams for intake of M.Tech students you can look into it.

You can give GATE in any stream irrespective of your branch, but will only get an M.Tech admission in that particular branch in which you have written your gate. But, you will not get a job in PSUS, because in PSUS, if you want to get a job as mechanical engineer you need to have a degree in mechanical engineering itself. So, if you are writing GATE in mechanical engineering to get a job as mechanical engineer in PSUS, then please don't do that, because you are not going to get that by any ways.

Yes, you can apply.

Yes, of course you can apply. Even final year students can apply for this exam.

Yes, it's part-time course and you can't apply for any PSU exam and you are eligible only for M.Tech.

The most important of all is self study. No matter, you join some coaching or not but the most of result depends on self effort. While preparing for GATE, it's important to only focus on the preparation. It will be a real challenge to clear GATE besides college/job. All the best.

Hello Abhishek, Unfortunately you have not mentioned the name of the course that you want to get admission into. But then generally speaking, getting admission in a particular college and branch depends on how those above you give their choice. Best wishes.