It depends colleges to colleges. Also branch change is not easy. there are certain terms and conditions like attendance, marks etc you need to fulfill to get your branch changed.

That you can ask from the college authorities in which you are interested to take admission.
Good Luck.

Branch change is little easy in same colleges like IIT BHU ,IIT bhuvaneshwar but in college like IIT roorkee,IIT kanpur u will have to secure atleast 9.5 cgpa and branch upgradation is offered in nearly all the colleges

It is possible in every colleges