Is it possible to change college after completing my second year in BTech?

Yes, you can change your college in second year but you cant do it in the national level colleges like NIT’s, IIT’s or the other deemed universities.
In local colleges you have the choice to change your college after securing fair percentage of marks. You need to apply to both the colleges for the change of your college to the respective college. They have to approve it and transfer your records from present college to the other. All you need to do is to secure good percentage of marks. Please remember this process wont be applicable for all the colleges across India. It is possible if both the colleges are under same university and the same state.