Dear Vishal,

if you get improved marks with new marks-sheet with 75% or more at the time of  councelling , then olny you will be eligible for IITs ,NITs and BITSATs.

if you are SC or ST then you will need only 65% to be elegible.

for more information please visit the website given below-

      https://engineering.careers360.com/articles/bitsat-eligibility-criteria

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

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

hope you understand 

thank you