Engineering

You can pursue any stream of your interest. A graduation degree is better, because in many of the jobs especially government one, a graduation degree is required. Whereas if you are more interested in chemical and want a career ahead in it then you should pursue it with no doubt.

Yes, you can get ECE.

There are good chances for getting a government seat.

The rank list for general last year was under 500 common rank.

You can get seat in Guru Nanak Engineering College. It is in the top 10.

IEM is best for cse because there is good placements for cse

Yes, you can get KIET with these score.

You can look for state engineering colleges accepting JEE Mains score. If you want to pursue engineering from IITs/NITs only than you can also go for one more attempt (if its your first attempt). If you want to do engineering than go for a state engineering institute and work hard. You can try for G

Based on your rank, you have good chances to get NITs like Hamirpur, Jaipur, Nagpur, Calicut, Patna, Tiruchirappalli. Other colleges where you have good chances are School of Planning and Architecture-Bhopal, BIT-Mesra, School of Planning and Architecture- Vijayawada.