Hello T Nagamani

Apply for lower branches (sciences,biotech,metallurgy,geology etc) in all old IITs.Give the order with importance to your wanted branch and their cutoffs by checking the previous year cutoffs.

You can also try giving options in new iits too,but possibility of getting core engineering branches is very low but not impossible.

If you are only interested in getting into IITs no matter what the branch is,then you are ok.But if you want to get a good branch specifically (like CS,Elec,Mech etc.),then I suggest to try again the next year.