Hi tushar.,
To get into IIT firstly ,you have to be eligible for the entrance.
Secondly you have to clear the minimum cutoff to qualify
Finally, you must be in top to compete for seat.
So here you are eligible for giving the exam after the improvements and not before.,

So it's clear that if you get a good score then you can get into IIT/NIT(score in mains)  in case you get above 75%.
Thank you.
For any other queries please do comment.

Hello Tushar,

Actually, you have to score 75% or in top 20 percentile in the 12th board examination after that only you can get an NIT college or give the JEE Advanced examination to get IITs.

For more information, you may visit the links given below

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

https://engineering.careers360.com/articles/jee-advanced-eligibility-criteria

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All the best.