Dear Romal,
Congrates for selection!!
You can get admission in old IITs .. you may not get the branch of your choice in IIT dellhi , bombay and kanpur .. but u ll surely get a good branch in old IIT..
regarding the best branch... i think all branches are best. It depends on how well u are able to understand, then u wont need to cram. and to understand, u need to simply have passion for what u are doing. so just clear ur mind and think of what u love best. dont compromise on that coz u got to live with it all ur life!
Click the link below link for opening and closing rank of IIT :
http://www.askiitians.com/iits-2009-2010-opening-and-closing-rank.aspx
Cutoff in new IITs check the link give below :
http://jee.iitd.ac.in/openclose09.htm (this link includes the more detail analysis)
for code of the cources check the councelling broucher 2009.
All the best