My first mains score is 86 percentile what should I do to get 100 percentile on second mains?Is it possible?

Hello Mukesh!

86 percentile is not  a safe zone to get a seat in NITs. It is not easy to achieve 100 percentile but you can score nearly 100 by following these steps :

Focus on those topics which have more weightage. Make a proper schedule. Focus on basic concepts and formulas in physics. Ncert chemistry is just like a bible, learnt them. Solve more sample papers and previous years question papers. Solve at least of thirty questions of Mathematics per day in given time. Take timed test series. Revision is most important, revise properly.

Good luck...