Are courses in DTU and NSIT flexible? Can students from lower branches study a minor in C.S. easily?

As an NSUT student, the new CBCS (choice based credit system) allows you to choose your fields of study. This makes for more flexible courses. Also, NSUT has an excellent coding environment which will help you for your minor in Computer Science. Many students over there pursue coding, despite being from a branch other than IT/COE. 

In DTU, you will have electives starting from 5th semester.These are department and general electives. IIIT Delhi offers the most flexible courses. Other than some fixed category credits, all the subjects are choice based. 

Thus, in terms of providing flexible courses, this is the order of preference- IIITD> NSUT>DTU.