From the s4 to the s6 - miss the menu key

[RyuAzuku99]

For my phone holding the back button does not open up the menu. I also have found to answer regarding if you can switch the S6 button layout (bottom physical button and the two either side of it) back to the original S4 layout? Is there any way to do so? I really hate it and want to immediately change out, especially since most of the apps I use do not have the 3 dot in app menu system. I have activated the dexterity help button but having it on the screen at all times is very annoying.

I also don't care if I have to root my phone to fix the buttons.

Summary: Holding back button does nothing/Is there anyway to change button layout from S6 to S4?