Colleges in West Bengal

What is the course fees for civil engineering after completing Diploma? Is there any scope for distant education? Is the institute AICTE approved?

As of now, just be consistent in your efforts and try to score as high as possible in CAT. That should be your prime focus. Interview and selection should be a secondary concern to you but I will mention a few insights.
10th and 12th marks are of concern but if you get the interview call, prepare we

No, due to the pandemic no college is opening right now. The college will reopen after the lockdown ends in India. So you should continue your previous studies for now.

The JEE Mains ranks below 200000 can be good enough for GNIT Kolkata in the asked course. The B.Tech course fee is about Rs 101,975 per year.

IEM is known for its placements. Lots of MNCs visit the college for placements and provide plenty of opportunities for students. The placement cell of IEM is very active and helps students in their placements. The average salary package offered is about INR 3 LPA to INR 4 LPA.