JEE Main

As you are eligible for Advanced, you should concentrate on that first.

yes you can get in gobind valabh pant engennring college garhwal uttarakhand.

Dont worry if you haven't done well in JEE mains,there are some private institutions that are doing equally good as top Government institutes.These institutes along with assured placements also provides an excellent platform to sharpen your skills.here are some of the colleges where you can get admission:
1.Lovely Professional University
2.SRM
3.BITS
these institutes conducts their own entrance examination to provide high scholarship.Lovely Professional University conducts its LPU-NEST and give scholarship upto 1.5 lakh based on the score in that examination.

Check the links below for rank and colleges:
https://www.resonance.ac.in/jee-main-answer-key-solutions/jee-main-2016-rank-predictor.php
https://www.shiksha.com/jee-mains-college-predictor

List of Top 10 CSE Colleges in India 2016:-
1. IIT Bombay
2. IIT Delhi
3. IIT Kharagpur
4. IIT Kanpur
5. IIT Madras
6. IIT Roorkee
7. IIT BHU Varanasi
8. ISM Dhanbad
9. Jadavpur University (Faculty of Engineering & Technology Kolkata
10. NIT Tiruchirappalli
Click on the following links sequentially:
https://www.shiksha.com/jee-mains-college-predictor

JEE Mains is for NIT's and IIIT's and JEE advance is for IIT, but to proceed to JEE Advance you need to clear JEE Main

yes you will get it easily
but if you don't want to take anykind of risk you can appear for JEE Advance

check it by shiksha rank predictor

to join anna university, u should have residential cerficate of the same state. and as i know about this university, u should apply for TNEA 2016 only then u can join.

No it is not possible