CBSE

Hello Jaskaran,
Repeating the boards will waste your 1 year. So, it will be better for you to take the improvement exam along with the preparation for various entrances.

Getting into Manav Rachna depends on your JEE Mains or UNI-GAUGE score. This college has excellent placements and companies like TCS and Accenture visit the campus for placements.

CBSE is better because JEE is also by CBSE.

Just keep your basics clear, you need to solve previous year exam papers. You must keep practicing writing the answers with all the answers written clearly (neither too short nor too lengthy) with appropriate diagrams. Your good presentation skill will definitely fetch you good marks and you can achieve your target.

If you appeared for JEE in 2016 and improvement in 2017 then last chance to appear for JEE is 2018.

I think, in all the 5 subjects.

You will only get admissions in private colleges demanding high donations.

After class 10th you need to go for 12th then you will be able to join college. For the best college you need to work hard in 12th. Score more to get admissions in Delhi University north campus colleges.