Yes, you can fill as many courses as you wish.. The larger the list the better is the chance of getting some course in an institute for a given rank.
You can check out the official site of IIT - D : http://jee.iitm.ac.in/counseling/
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 for your future!