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apps wont open facebook, viber, yahoomessenger, and instagram
Did you already try to reset your phone by holding the sleep and home button for about 10sec, until the Apple logo comes back again? You will not lose data by resetting your device.
If this does not work, set it up as new device:
Don't do any of that until you have downloaded and installed any free program from the App Store. Easier and far less work.

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