Games on iPhone and iPad are different. They are not compatible with each other and there is no opportunity to transfer the game progress or synchronize them. Please, note that this feature is not a whim of developers, this is the result of system requirements of an application for platform devices.
The iTunes/iCloud backup option also allows transferring game progress only from iPad to iPad and from iPhone to iPhone. You can find more information about the option here: http://support.apple.com/kb/HT1766
These games also use different social servers, so there is no opportunity to add friends who play on a different platform.
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