How do I downgrade from Lollipop back to KitKat on Micromax Yureka I am having the problem of many application not responding on my Micromax Yureka after upgrading Lollipop Android 5.0. My phone hangs a lot I want to revert back to KitKat.

It was working flawlessley in KitKat. Also, the screen diplay disappers when a call is going on, because of which I am unable to decline the call
When I searched Google with "micromax yureka kitkat ROM", the very first link was a YouTube video explaining all nicely.

It explains by getting the ROM from XDA and further instructions are available at that page.