I am not getting the line '3 years i am interested in iit  if I change my board'. Please elaborate to get a better answer.

As a general answer : Yes state boards are leigible for IIT and evwn if you change your board from CBSE to State Board you will be eligible beacuse IIT only wants your 12th marksheet and it will not matter that you changed your board in 12 th. But the challenge is to change the board. In my knowledge uts quiet tuff to change your board jn class 12th.
But if you are able to change the board then also you are eligible.