dear aspirant,

according to the guidlines of jee main 75% is mandatory to seat in the exam of jee advance.

if you have achieved the score of 91 percentile then you can seat in jee advance but you have to pactice more and more and have to learn the concept very carefully to crack the jee advance and get the IITS

but if you will not get the IITS unfortunately , dont feel stressed you can get nits according to your rank easily, so stay focussed with the relaxed mind.

good luck