How can i update ibooks and youtube when someone else is signed in already on my iphone4?
If someone else downloaded the apps under their AppleID, then you would need to know their password in order to download the updates.
If the apps are free (YouTube) just download them under your own ID.
Tap on the iTunes icon, scroll to the bottom, tap on the Apple ID link, tap on sign out, then log on with your ID.
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