M.A

It is a very good idea. Firstly, you have to do the primary teacher's training certificate as PTT, BTC, D. El. Ed., and B. El. Ed etc. After that, you have to clear TET exam either CTET or state TET. And you must be selected in merit list.

Only IELTS is enough. You do not have to do GRE.

You can contact your university/college from where you have done MA and ask them for the procedure of getting new/duplicate certificate. There you would get a new/duplicate certificate by filling up some forms and paying the required fee.

The last date to apply for June 30.

In the NET exam, you need to select the same subjects in which you have done your post-graduation. You can't choose Urdu after doing M.A. In economics.

Yes, you can. Contact local IGNOU center for details on admission and fee. It is legal and accepted widely.

There are total of 46 seats.

It will be declared soon. Keep checking the updates section on: http://www.amucontrollerexams.com/.

There are approximately 50 seats.

Hello Uday,
I can understand your angst for missing 50% mark by just few marks. But do not worry. Many universities allow students with 45% marks to appear for entrance exam for admission into PG courses. For NEHU, unfortunately I couldn't locate any such restriction. However I am attaching a link that will give you all the required information about NEHU and also helpline number.
https://nehu.ac.in/Admission-2018