Can I do ICT after btech in mechanical
Yes, you definitely can, and when you aim for it, you must gather a lot of basic knowledge about computers just in case you don't feel that words uttered in classes are alien to you. A bit of microprocessor, linux, kernels, structures etc. That will help you understand. In short, learn the language of guys from CS. Apply for GATE examinations and get a good score in CSE and you'll definitely be where you want yourself to be - In the CSE Classroom of an IIT as a student.