Chemical Engineering

Yes doing instrumentation engineering is better than chemical engineering in IIT, kharagpur. But You may not getting government job directly it needs cracking competitive exams Organised by upsc.

If you belong to OC and Arulmigu Meenakshi Amman College of Engineering is the best.
If you belong to BC, Arunai Engineering College is the best.
If you belong to MBC, Vel Tech High Tech Dr.Rangarajan Dr.Sagunthala Engineering College is the best.

It's better to go for ECE from NIT-Silchar rather to go for chemical from NIT-Raipur.
As both the colleges are not topped ranked NITs, so here branch matters more than the college.

If you do not have any personal constraints then lateral entry B.Tech chemical engineering is the best option for you. You may also evaluate doing AMIE along with job after Diploma in chemical engineering.

Placements of chemical engineering are better than other branches of engineering.

In my view, you should join B.Tech. For this, Jaipur is the best place for engineering. NIT-Jaipur is the best college. But MNIT does not prefer such kind of Diploma students. They take admission through JEE exam. So, you can try for SKIT, JEREC, Anand International College of Engineering College, e