What are options for power button I have Moto E (2nd Generation Android version 5.0.2) .I use power ON/OFF button to lock the smartphone phone or to go into the sleep mode.
Due to frequent use of power ON button, the switch is not working properly.It needs to press it long and hard.

So are there other options available except power button 

1.To lock the smartphone

2.To make smartphone go into sleep mode.
and

3.To turn ON the smartphone.
You can use apps like.   https://play.google.com/store/apps/details?id=com.enlace.doubletap

For sleep or wake this app works pretty well but I don't suppose if it's ever possible to power on the phone with an app installed in it and phone is switched OFF.