Answer by iCodeAtApple for "The iPhone could not be synced because this computer is no longer authorized for purchased items that are on this iPhone:

I almost had the same query and wanted to test the iPA asap.So perhaps this would be the answer to you second question which is installing the iPA without the iTunes :

Try to install the IPA from Organizer instead of iTunes. To do it open Organizer from: Xcode > Window > Organizer, then select Applications under your device and click the + button to add the IPA.

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