I have been developing my gaming app using game salad engine, after releasing my app i decided to change to unity for several reasons, is it possible to change the game build after releasing with a totally new build using a new engine? and does this affect Non-Consumable in app purchases that people already did?
You certainly can. just rebuild the game in unity, and I mean create it again.
For non-consumables iaps, you will have to make a Restore Purchases button, which is easy in Unity.
This is a tutorial for IAPs on Unity.