Which IIT has the most liberal branch change rules (apart from Mandi and Gandhinagar)?

IIT Guwahati might be a good choice if you are looking for a branch change. You will be allowed a branch change with a lower CGPA at Guwahati compared to other IITs. It is always better to first opt for the branch you are interested in. The competition level is very high for a branch change, especially in reputed institutions like IIT Mandi, and you need to strive hard for a branch change. So you can go with the option of IIT Guwahati.