how much you willing to pay
j/k:rofl
just uninstall 11 but keep your settings folder somewhere, and you skins unless you want to wait again for all the skins. delete the rest of hct files
then install patch 4 again (complete version) then go back up the latter of patches all the way to 10, then put the settings and skins folders back in the new htc folder.
try searching news and announcements bb and go back 100 days