Signing Out of iCloud or Apple ID
Ankur Thakur (via Dave Mark):
This tutorial shows you the steps to sign out of iCloud and your Apple ID (both are the same) on your iPhone, iPad, Apple Watch, and Mac.
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Here’s what happens when you sign out of iCloud or Apple ID. Please note that the consequences are limited to that device only. You can continue to use the iCloud services on your other devices.
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Here’s a list of services you can no longer use.
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After you sign out of Apple ID or iCloud, App Store, iMessage, and FaceTime are also signed out automatically. But you can still activate iMessage and FaceTime using your phone number. You cannot use your Apple ID email.