Brother JEE advanced admits it's student who are top 20%ile in their respective X11 boards. Also for admitting at IIT, JEE advanced allows you to give only two attempts. 

Also JEE advanced considers first attempt, the X11 board year and the next one would be following year from X11 board. 

Also for JEE advanced their is no need of doing any diploma.

I hope I've made the things quite clear.

Thank You