Colleges in Ahmedabad

As mentioned in your question, you can give a shot at NMIMS Bengaluru. However, that is a little costly institute but a decent one. BK School of Management is average. Considering the fact that most of the B-Schools have already started with the 2019 session, you need to look for colleges that are still taking admissions. Else, try for next year.

No, you should be registered for the admission in any college.

My advice would be to never miss on the admission form of any college because you never know when your luck comes in handy and secures you a seat. So, at least fill the form and give a try to your luck. You might actually get a seat. Because you score seems to be fair.

You may go to this link you will get everything here https://www.shiksha.com/college/poona-institute-of-management-sciences-and-entrepreneurship-camp-pune-22295

A career after civil engineering is highly rewarding. There are jobs that involve supervision, construction, design and analyzes of private as well as public projects, such as dams, highways, canals, water sewages and bridges. Excellence and responsibility are important factors associated with the job.

Hello Ayushi, the typical Shakespearen dilemma! Do not worry. Both chemical engineering and CSE have a great future. In short term, graduates in CSE gets more pay & attention but in the longer run, it evens out. However, I would like to advise you sincerely that, your criteria for selection should not be money but fascination for a subject. Then study becomes happiness and one enjoys whole course. Please do mediate, think, discuss and then only select.
Best wishes to you.

Both of the institution is better according to nirf ranking

Hello Samiksha,
That depends on your graduation results rather than on 10 or 12th, so work hard in coming years. For further information, you can refer to the link below:
https://www.shiksha.com/college/iim-Ahmedabad-indian-institute-of-management-iima-vastrapur-307/admission
All the best.