How to downgrade from Marshmallow to Lollipop in Micromax Canvas A1

A few days back I upgraded my device from Lollipop to Marshmallow and facing a lot of issues since then.
Some of them are:
1. Phone gets hanged while trying to receive an incoming call.
2. Phone gets heated while doing nothing.
3. Battery drains faster than ever.
4. If someone's trying to call it would take longer than usual to connect.

Can someone tell me the steps to go back to Lollipop from Marshmallow?


Thanks,
Girish