the OS of the phone is indeed untouched. only the icons are changed and some other files.

a debranded phone works as good (if not BETTER) then a branded phone

i don't know what you are talking about on the joystick. i had a K750 and i know have a k800 and i didn't had any problems with the joysticks. just be carefull and clean them sometimes

to do all that with your phone you will need FAR manager of XS++ (only for CID52 or lower)