Dear Aspirant,

Once you give the JEE main then there will be the JEE advanced if you qualify mains and eligible for Advanced. Then once the result of the Advanced is declared, then only the councelling procedure is started. In the councelling you will be shown all the colleges you can select, if you cleared only mains, then only NITs, IIITs and GFTIs will be shown. If you have cleared the JEE Advanced then you will be shown IITs too, along with the aforementioned institutes.

Hope this helps. Thank you.