CBSE 12th

You need to clear off your higher secondary first then you can think to pursue further.

MINIMUM ELIGIBILITY REQUIREMENTS: Passed 10+2 or equivalent Examination securing a minimum of 50% marks in the aggregate in the subjects Physics, Chemistry plus any one of the following: Biology, Geology and Geography and must have passed in each of the concerned three subjects (as supported by the Certificate issued by the Examining body).AGE: Age should not be more than 22 years on 1st July of the admission year.

In order to crack IITs, you need to have more than 90s and specifically in higher ranges and if not then atleast more than 75% but it would not work.

Yes, you will be eligible provided you pass all the three exams and then you need to secure 60 percent overall in order to get a chance to be eligible and you can sit in 2020.

Percentile should be under top 20 and must score atleast 75% marks. This is what have mentioned online. Its better to find out the college and check the eligibility accordingly.

You must have atleast 55% marks in your 12th for the entrance purpose in any undergrad course.

https://www.shiksha.com/courses-after-12th
Here is a blog from which you can choose your career according to your interests.

You can easily go for BCA here, as the gap will be considered after your higher secondary. So go and find the college suitable for you. as per the region and place.