Hi aspirant

If you got admission in ECM for b-tech then after first year you can change your branch as you want CSE. For changing the branch they check your attendance and results ( as the University want like 8.5 or 8.0 CGPA) .And it possible when your college have vacant seats for the branch you want otherwise not . Also you can get the chance to M-tech in CSE after pursue b-tech in any other branch. But that is difficult enough to give the gate  exam in CSE as you doing b-tech in ECE.

I hope it helps you.

Best wishes.