JEE Main

It depend, in which stream you want to take admission. But, approximately you need 170 marks for top NITs.

It depends in which college you want to take admission.

Yes, you have chances in physical counselling.

Hi Lakshya,
You can use the college predictor link to find suitable colleges as per your grades and rank
https://www.shiksha.com/jee-mains-college-predictor
https://www.resonance.ac.in/reso/news/JEE-Main-Branch-Predictor.aspx

Yes, minimum 75% in class 12th is the eligibility criteria for JEE mains. JEE mains can help you to get admission in NITs and IIITs. Once you clear the cutoff for JEE main, you are eligible for JEE advance. JEE advance is the entrance exam for IITs and ISMs.

By preparing and of course scoring well in JEE main, you can get admission in NITs, but to get admission in IIT you have to first score well in JEE main and required 75% marks in class 12th. Then you are eligible for appearing in JEE advance examination. If you score well in this exam, you can get admission for IIT. To get admission in IIT, you have to do smart work and it's totally different from the preparation of JEE main exam.

In 17 mark, you can't get any college, but you can apply for private college. If you wanted to study in best college then take a drop and prepare for class 12 and different entrance exam as JEE mains, BITSAT, VITEE, etc.

According to this year cut off, you need to score around 180-195 marks to get rank below 10,000.

Yes, you can get colleges like DTU, NSIT or IIITD.

It depends on the normalized score, which will predict your rank.