I would be thankful if anyone can suggest a solution to do this
There are actually a couple different ways to do it...
You can used Xposed mod, with either Xposed Additions or MenuBeGone
(I've never used either of these methods...)
or, the way that I do it, manually edit the \system\usr\keylayout\Generic.kl file.
When I do it, I make the following two changes:
Change key 139 from MENU to BACK
Change key 158 from BACK to APP_SWITCH
Then I use button savior to add the menu for those things that need it...
(I'm coming from Nexus devices, so having the keys with back on the left, and app switch on the right is how I'm used to it...)