MCA

Average salary would be between 2.5 to 4 lpa. Companies that visit the center are as follows:
TCS, Evosys, Streebo, Elite Core,Zensar and many more.

If you are able to clear or reappear in subject in which you have failed in 5th semester before start of MCA then you are eligible for seeking admission in MCA. Some universities might give you provisional admission subject to clearing BCA by their published date of submission of documents.

10+2 with maths as one of the subject and degree with maths and any B.Tech course or BCA.

Surely, you can. If you have sound technical knowledge, after 1 year of professional experience companies focus more on your work then your marks in a particular course.

Nirma is undoubtedly a better option in terms of faculty and placements.

I think instead for going for a course, you should join a company and start working as only then you will be able to gain sound practical knowledge, pursuing a course after MCA won't help you much.

Of course you can, you over eligible for PGDCA course.

It's a good choice, to confirm check the reviews below:
https://www.shiksha.com/college/institute-of-industrial-and-computer-management-and-research-iicmr-nigdi-pune-36653/reviews

Dear,
So far my knowledge goes for doing MCA, BCA is not the only path. You can do MCA after doing B.Sc.in maths/ physics/ computer science. For admission in MCA in your targetted university, you have to check their eligibility criteria.
Best wishes!

Hello Shubham,
Vellore Institute of Technology (VIT Vellore) is a good college for MCA. It has a huge reputation and offers a better education.
So you may get a good knowledge, exposure and placements at VIT Vellore.