North Eastern Hill University, Shillong

Hello Dipak,
As per my knowledge, I think you want to apply for Mtech in Environmental Engineering after doing your Btech in Civil Engineering. You need to appear for the GATE examination for that. But our University does not provide such courses. You can check from this site the list of technical courses provided by our University: https://nehu.ac.in/school/5/School-of-Technology
But if you want to apply for MSc in Environmental science, it is under the school of Human and Environmental science. The Candidates with a Bachelor's degree (Majors) in Environmental Science /Botany /Zoology /Chemistry / Biotechnology /Biochemistry /Geography /Geology/Forestry are eligible to apply. You need to apply for the NEHU Entrance examination. Last year the last date to apply for MSc in environmental science was 16th July 2019 but this year it hasn't started yet. You can frequent;y check their website for further admission related details: https://nehu.ac.in/Admission-Announcements
But I am not sure whether you are eligible or not for this course, you can search for further information from google but surely you can apply for Mtech in Environmental engineering but in other colleges, because it is not provided here.
Just a suggestion I think you should apply since it depends on the university because an engineering degree is a bit enough for this course.
Hopefully, my answer help you a little bit
Regard

EDIT: Admission to general courses has started. Fill the form quickly. The last date is 24 Nov 2020.
https://nehu.ac.in/public/uploads/Admission-notice-Gen-PG-Ph.D-2020-21.pdf
Hello Mekha,
This is the link for ongoing admissions in NEHU: https://nehu.ac.in/Professional-Courses
Plus you should frequently check thE announcements site of NEHU to get the proper admission dates of your desired course: https://nehu.ac.in/Admission-Announcements
In the last year 2019, the last date to apply for M.com admission was 16th July 2019. But this year everything is late so till now there is no news for m.com admissions. So I'll suggest you wait for university notice and check their sites frequently.
and you should check their admission dates for general courses particularly from here: https://nehu.ac.in/Admission-2019#collapseTwo

EDIT: Admission to general courses has started. Fill the form quickly. The last date is 24 Nov 2020.
https://nehu.ac.in/public/uploads/Admission-notice-Gen-PG-Ph.D-2020-21.pdf
Hello,
Usually, application forms for M.A. End by the month of May or June, although am not totally clear about the starting dates. I'll suggest you check the official websites and its announcements for upcoming admission details from January to July. In the upcoming year 2021, they will surely drop the admission related announcements there. You can check from this link:
https://nehru.ac.in/Professional-Courses
and you should frequently check there announcement broad from here:
https://nehru.ac.in/announcement
Regards.

Yes, you can get into it with these scores. The eligibility criteria to get admission in BTech ECE is just to have 45%in 12th with PCM also with a minimum of 45% marks in each subject and should have cleared JEE mains with valid scores and rank. JEE mains marks are considered for the admission round. All students were categorized and listed in a particular manner based upon their overall score of 12th and JEE according to which they are called for their branch choices. Simply it is like a student with good marks are preferred first, they get the chance to chooses their desired branch. We have 4 branches in UG BTech with a maximum intake of only 60 students. So if the ece branch is full before announcing your name, you may not get admitted to ECE. But surely you can have other branches.
Good Luck to you!
You can check the eligibility criteria from this link: https://www.shiksha.com/b-tech/course/b-tech-in-electronics-and-communication-engineering-north-eastern-hill-university-nehu-shillong-314291
and for more information you can refer to this link: https://nehu.ac.in/school/5/School-of-Technology