Colleges in Allahabad

Completely depends on your interest.

Very rare chance. Choose some other branches like biotech and get a decent CPI in the first year. Then you will get a chance to change your branch.

Very rare chance since you are from general category.
Go for some other branches like chemical, biotech and with a good CPI in the first year, you can change your branch.

Not a doubt, MNNIT Allahabad CSE. See placement records at www.academics.mnnit.ac.in
From my experience, I can say that coding culture at MNNIT is awesome.

CBSE class 11th and 12th Maths should be on your tips for B.Sc maths entrance 2018.

It totally depends on you and your choice of course and your interest in a particular field. If you are into coding and developing, DA is the choice to go because the coding culture is raved at DA. I do not know about the other colleges but I do know as a matter of fact that the course options that you have given for the other colleges, all of them come under ICT in DA. You can choose, electronics, communication theory or coding or computing when you take ICT. Hope this helps.

First, it depends on your interest level on the Branch. Next, is the duration of course. Are you okay to spend around 5+ years in the same course, and specialization at a stretch? If you are inclined to take up career in IT and Data-Science, Machine learning etc., then better opt for integrated course. ECE will be a bit tough, when compared to IT, and if you are very keen to go for ECE related jobs, then you can opt ECE from ISM. Keeping in view of placement opportunity and coding environment, it would be better if you to go for IIIT integrated course.

Hello Chinmay,
Among all the colleges, you have listed above Information technology at IIIT Allahabad is much more better option than any other, because IIIT Allahabad is very much known for its excellent teaching and superb placements records.
Best wishes.