hello, I have the same problem on a S4,
home button works but back button and options do not.
I changed the display, the entire display, so I did not remove the screen or anything. could be that I damaged some cables during the process? any idea on how to proceed? the daughter board would be that little extra piece at the button with the 4 screws?
I have a blue cable in there, I guess bring power to the buttons, the home button works so that cable should be ok right? what else can be damaged?
thanks a lot!