NIIT University

Hi Sachin,
As per your score in JEE Mains exam, you can't get admission in computer science engineering in any NIT. You should go for private colleges like Amity University, Sharda University, Lovely Professional University, LNCT Bhopal, Techno India Kolkata, etc. You can also predict other possible colleges here:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Both are best. The first point is that your area of interest towards the subject. B.Com is a 3 years course while integrated MBA is 4 years course. If you are interested in Entrepreneurship, Marketing, Management, Finance etc.you can apply for an MBA.

If you have the time, and if you are highly confident that you will get into Iims, you can pursue BBA and later get some work experience and finally write CAT to get into IIM. If you don't think, this is all going to work, just go with it.

https://www.shiksha.com/b-tech/resources/jee-main-rank-predictor check here rank and college cutoff and get the opening and closing rank for the expected college. With this rank, your eligibility is less but hopefully, you can achieve that in the 2nd round.

Both the universities are great.
I do not have much knowledge regarding the course.
But, both the universities are good and according to me.
NIIT University is better for B.Tech as compared to Amity University, Noida.

Yes, it is. NIIT regardless of the region is recognized. Depending on the particular university an additional evaluation may be required, but it is not too complicated and will be told by the university. Please write to them and check directly.

Yes, this university is recognized for government. /PSU Jobs.

You can directly approach the college for admission in Diploma in chemical engineering. There is no entrance exam.