I am using lyf water 7 with stock android marshmallow. Whenever i click on menu button first the recent apps screen opens up and then menu. I tried factory reset but it didn't work.
Welcome to Android Central! Which menu button are you referring to? One of the capacitative buttons next to the physical Home button? It's been a long time since either of those buttons acted as a Menu button. It's standard now that one of the buttons is Recent Apps and the other one is Back.