NIT

No, you can not join NITs after clearing NERIST
The NERIST Entrance Examination (NEE) is conducted by North Eastern Regional Institute of Science And Technology NERIST for admissions to various B.Tech programmes, offered by NERIST. The entrance examination is conducted at different centres in the State of Arunachal Pradesh, Assam, Meghalaya, Manipur, Mizoram, Nagaland, Sikkim, and Tripura. For more details check the link below:
https://www.shiksha.com/university/north-eastern-regional-institute-of-science-and-technology/exams/nerist-entrance-exam.

There aredifferent cut-offs for different categories but if your score is above 150, you will definitely get a good college.

You need to take minimum 75 marks in JEE Mains to eligible for NIT Colleges.

Yes, you can get. Contact the respective colleges ASAP.

As a general category, you must score minimum off 275 + to get admission.

To predict your college please go through this link, it will provide you the details of colleges which you can get -
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor.

Hi Karan Raj,
It depends where abroad you are planning to study. NIT is among the best in India for technical studies. And if you are going abroad you have to see if it's a good college. You can compare and then decide.