NIT

One should have scored at least 75% marks in class 12th examination. Apart from this, there is no other condition of 12th board percentage is required for admission in NITs and IIITs. And also there is no any official benefit of having a good percentage in 12th.

Hello Veman,
To get admission at NITs or IITs, you are required to have a good score in JEE Mains and Advanced. But, it is mandatory that you have a minimum of 75% (for reserved categories) or 65% ( for unreserved categories) in board exams to be eligible for the admission. Even if you have a top rank in JEE exams, if your score in boards is not as required, then you will not be able to get a seat.

Hello Ayushi,
You may use the college predictor tool from the link below to know your chances of getting a seat at NITs and the other government colleges:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Yes, but you have to give the improvement exam for all the five subjects of your 12th class. Only then your improved score would be considered otherwise your original score (unimproved) will be considered for the admissions.
Best of luck.

Though, Advance will not affect your NIT admissions and so the JEE Mains will do. Kindly mention your JEE Mains marks and category to get the possible choices of college for you.

Considering, you're from general category, you won't get old NITs with these core branches unless you have home state quota. In new NITs, you can easily get the core branches also apply to Delhi college counselling because with this rank you also have opportunities for NSIT DCE and IIIT Delhi and those are also good colleges. Also, check out Shiksha's rank predictor.
All the best.

Visit the link below to find the colleges on the basis of your rank:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

Yes, you can get NIT, but wait till June 10 when JEE Advanced results will be declared.

For your answer, I am providing you a link. Please insert the AIR and the list of colleges that you might be getting on the basis of your rank will appear-
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor
Hope your query is resolved.
Best of luck.
For any other query, please feel free to ask me.