Just a few random things from searches.
wifi direct htc one m8
This is described HERE, and that method works on pretty much all current HTC phones (and Nexus devices).
switching to art in htc one m7
Not currently possible, I assume it will be a part of the Lollipop update since ART is the default runtime there.
my htc one just updated to 4.3 is there a way to change the green color
Simply put: No, since that is a design requirement from Google (Android is their product). And battery icon is simply the colour that Google wants it. And for the moment it’s white.
wipe cache partition htc one
You’ve got a full set of instructions on that HERE.
htc polish language
If you don’t find the language you wan to use, and your phone runs 4.2 and higher. Then you must use the instructions found HERE.