Will I be able to handle another college along with IIT-M BSc Data Science or will it be difficult? Moreover if I complete BS after 4 years I this can I do MS in IITM in offline?

The IITM BSc Data Science Program has a very flexible structure. It has 3 terms a year and has no mandatory attendance; rather, attendance is measured through the submission of weekly assignments. According to the institute, the estimated time required to do fairly well on the course is around 10 hours per week which is an achievable goal for students who are already enrolled in another degree program.

The program is designed to be accessible to as many people as possible and the only strict requirements are the in-person, proctored exams that students have to write at centres near them. The list of exam cities can be found here: https://onlinedegree.iitm.ac.in/academics.html#AC9

It is yet unclear whether the BS program is offline or online but once you complete your four-year BS degree, you are not automatically eligible for any postgraduate degree at IITM.