Dear Payal ,
There are chances that you can get old IIT's .. but the problem is u may not get the branch of your choice. And in between NIT and New IITs .. you should go for NIT's coz it will take some more time for the complete development of New IIT's and NITs are old and completlty developed in terms of education and infrastructure...
Please feel free to post as many doubts on our disucssion forum as you can. If you find any question difficult to understand - post it here and we will get you the answer and detailed solution very quickly. We are all IITians and here to help you in your IIT JEE preparation.
All the Best .
Amit - IT BHU