Is there any restriction for filling up number of choices of Institutions (Colleges) or subjectsin choice filling form?

No, you can give as many choices as you wish. However, choices should be in order of preference, as the allotment is done on the basis of choices submitted by the qualified candidate in order of preference given by the candidate and as per availability.

However, it is advisable that the participating candidates fill-in the choices up to a total of 30-40 choices.