desktop cube and gnome 3.4

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http://askubuntu.com – i have installed compiz settings through ubuntu software center and i have enabled the desktop cube and desktop rotation but when i tried to rotate the desktop it is not working. i have also installed gnome 3.4 but i am getting the gnome classic desktop instead of gnome3.4 even though i am selecting GNOME at login and i didn't installed gnome games plugins because i was not able to download them (HowTos)