Hello Udaya,

Getting a free seat in IIT and NIT doesn't depend on the score all the rank to secure in either JEE mains for JEE advanced.

Even it be student who secured 1st rank in JEE advanced cannot get a free seat in NIT or IIT is unless considering the following points.

Students parent income must be less than 2 lacs per annum and he must pursue a economically backward class certificate from his state government.

Economically backward class certificate is given by the respective state governments to the students whose family income is less than 2 lacs per annum once you secure a seat in NIT or IIT and if your family income is less than 2 lacs per annum you can get an economically backward certificate and put it in your application form while applying for the respective IIT and NIT is to get a free seat.