Techno India University

Techno, Rajarghat is an average college with not so good placements, I would recommend you to join some other better college:
For details, check out the link below
https://www.shiksha.com/college/techno-india-college-of-technology-rajarhat-kolkata-48632

Since both the colleges are private college and share the same campus, so the deciding factor here is placement records and as per placement records Techno India Salt lake is better than Techno India University.
You can also guess from the WBJEE opening and closing rankings for both the colleges.
Hope, you got your answer.

Hello Shubham,
As per your college choices, it will be better for you to move forward with CSE at Sant Longowal because colleges in Kolkata are not very much known for their exposure and placements, so opt for Longowal for better exposure and placements.
All the best!

For getting into private universities they keep entrance exams wherein you should apply for them else you can also try for management quota.

You need to check this with the college itself.

You surely can. MBA can be done by anyone and in any specialization. Engineers go on to do MBA in finance, which is not even their field.