How do I restore the iPhone’s firmware to the version I want instead of the newest version in iTunes?
To choose the version hold down the shift key (option key on macs) and then select restore. This will open a window to allow you to choose a file to restore the iPhone with. Your options will be located in the $:\Documents and Settings\your-user-name\application data\apple computer\itunes\iphone software updates\ (library/itunes/iphonesoftwareupdates on macs) folder.