Enable multi-user feature on your Android one phone (running Android 5.1 Lollipop) without flashing .zip through custom recovery. All you need is root access.
Just go to /system , edit your "build.prop" file and add the following lines:
fw.max_users=3
fw.show_multiuserui=1
fw.show_multiuserui=1
Save and reboot your phone. Done! Tested on Micromax Canvas A1.