Exam

Yes, the ranks for JEE main and that of JEE Advanced will remain the same for JoSAA counselling. You need to choose your category and then you should see you rank.
The link below gives you the previous year closing and opening ranks for each NIT, IIT, IIIT and GFTI:
http://josaa.nic.in/Result2016/res

Chances are less for getting admission in ECE at Institute of Technology, Nirma University, Ahmedabad. But you can try for it and yes, of course, it will give you a very good career.

No, you should have more than 75% marks in class 12th boards or you should be in top 20 percentile.

You can check the opening and closing rank for general category by doing some Google Search. I think you have less chances but don't lose your hope and hope for the best.

No you wont be able to get in BKSBM without CMAT.

There are total 2 attempts to appear for BITSAT. So if you have missed then you can only appear in 2018.

Yes, GMAT is mandatory and along with GMAT you have to have at least 3 years of work organisation in an organisation and also need to have minimum 6.5 IELTS score and at least a 4 years Bachelor's degree such as engineering or a Master's degree with good academic record.

Reva is very bad college. It has very low placements. But college doesn't decide your future. Work hard where ever you are and you'll ultimately succeed.