CBSE 12th

Your academic performance looks impressive and in my opinion you should get a GD/PI call from IIMA if you secure more than 99 percentile.

I am not sure as you would be borderline case for all IIMs and other top colleges. And also as soon as results are out, shortlists are announced. Hence you should not worry about the interview calls. I would suggest you to focus on the CAT and do your best.

Pursue a vocational course in an area of your interest , upgrade your specific skills and seek a job opportunity.
Prepare for government clerical position exams & explore a career in government service.
Retail industry also has a lot of opportunity for HSc students

Depends purely on which category you belong to.General category people have to suffer a lot inspite of being far more meritorious than their counterparts belonging to the reserved category, and that is really sad. In case you are a general category student, you need to score around 95% in boards and a bit higher in mains to get admission in any branch of NSIT.

The cutoffs for ST category go up to 84,000 for Delhiites and about 32k for outside Delhi students. So, if you are a Delhiite you may comfortably get admission in NSIT even if you score about 90% in boards and say, a 100 in JEE mains. Or maybe you can get admission at a score below that too.

I think anybody can go for NEBOSH diplomas. To be more sure please mail to information@nebosh.org.uk.

No not at all, it's a myth that USA has issues if you have gap in your studies. It has well said in previous answers if you have been able to demonstrate your gap well in you SOP it won't have any issues whatsoever. for USA visa key is demonstrating your intentions well along with your research work about course and college you are applying for .

It may help in increasing the percentage overall.
If the marks is less in any subject then it is interchanged with the additional subject.
It also increases our knowledge .
(May be somewhat it will help you.)

Follow the predictor below to check :
https://www.shiksha.com/kcet-college-predictor