India

WBJEE 2018 College Predictor. Use your WBJEE 2018 rank to see where you can get admission at the link provided below. See the courses, colleges & rounds you may crack. The result is based on admissions data of WBJEE 2017. Get resources & insights on colleges & courses:
https://www.shiksha.com/b-tech/resources/wbjee-college-predictor

Which course are you planning to pursue and where? It is totally at the discretion of the college.

https://googleweblight.com/i?u=https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor&grqid=YfMRDoqA&s=1&hl=en-IN
Please, go to the college predictor link I am sharing here to know about the college you can get.
Or you can check here.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
Good luck.

No, you will not get admission. Also, with these marks, you are likely to get into one of the big private universities. Kindly apply for that. Some recommendations be LPU, Amity, CU, VIT and SRM. These colleges have their separate entrances, though.

There is no eligiblity criteria as such. Its just that you should have scored well in English and overall you should score good percentage as if you opt Delhi University. It's best for B.A. Hons english with effective study. Good faculty with less fees however fee may be varies from college to college. It's just that you may eligible for the cut off of Delhi University. In private universities, Amity is the best. Here is the details regarding Amity University:
https://www.shiksha.com/humanities-social-sciences/languages/course/b-a-hons-in-english-amity-university-Noida-207080
Hope this helps.

Yes, you need a migration certificate.

It is quite tough, though not impossible as JJ COA accepts for top students with rankings below 500. Moreover, you still can apply as you stand somewhere there only. Also, you will easily get NIT trichy which is also a good college with the same reputation as JJCOA.

If you have Biology as your main subject, you may go for B.Sc. Biology.
Else, pursue other subjects which you think you are good at.
Never get dejected.