What are the prerequisites for IT in IIIT Allahabad?

There are no such specific prerequisites. You can develop an interest in coding within one year if you are interested.

The programming courses in the first year entail the comprehensive usage of C. It definitely is an extensive course and will take up time. You will learn the basics of it in the first year. The course includes parts like Functions, Pointers, Linked Lists, Data Structures, Object-Oriented Programming, etc.

Although, having knowledge of Python helps. If, however, you've arrived with no knowledge at all of what that is, then it is fine too. Classroom teaching does not help that much for learning to code. Mostly, you will need to learn the aspects of this language with your own efforts.

If you have any spare time, learning basic front-end web development will assist in the long run as well, like HTML, CSS, JQuery, and Javascript (If possible). This will help explore a variety of other opportunities outside your curriculum.