Flash menu's do work on K800i if you flash it with W850i's firmwire, but the majority of the K800i doesn't work like Camera, joystick and the m2 stick.
Kinda ruins it then doesn't it? Who'd want to go from 3.2mp + af to 2.0mp with no af? Even if you do get walkman v2 + flash themes. It's not worth the trade-off.