Colleges in Kolkata

Amity University, Gwalior is a private university located in Madhya Pradesh. It is accredited Grade A by the NAAC. Amity Gwalior offers B.Tech course in total 9 specializations. The candidates who are willing to apply for this course must have scored at least 60% in Chemistry, Math, Physics, and English combined in 10+2.
The eligible candidates can apply for Amity JEE exam. The selection of the candidate would be done on the basis of the score obtained by the candidate. The will followed by a test on the day of the interview.
Direct admission is also done on the basis of a valid score in JEE Main.

https://www.shiksha.com/b-tech/course/b-tech-in-bio-technology-techno-india-university-salt-lake-city-kolkata-200973
Refer the above mentioned link.

No, you won't get CSE in Heritage. Try for other branches.

You need to have 50% and above for admission in this college and course.

You need to have 12th from a recognized board with minimum 50% marks.

In Kolkata the list of top 10 college are:-
Jadavpur University
IEM
Heritage
Techno India Salt Lake
St. Thomas
RCCIT
Techno Rajarhat
BPPIMT.

Chennai is better.for its placements although you should also have a good rank

Jadavpur University is a State University of West Bengal and thus the admission is done through WBJEE, Jadavpur University doesn't take admissions through JEE Mains.
So, if you want to get into Jadavpur University, first sit for WBJEE.
To get into JU, you need to get a rank under 1500, if you are going for Electronics, CSE, Mechanical, Civil, Instrumentation etc., then you need a very decent score, your rank should be under 600700. But, if you want to get in IT, Power, Printing, Construction –etc, then scoring under 12001500 will be enough.