iPhone X and iTunes 12.7.3

Starting with iOS 11.3 beta 2, users performing tethered updates or restores on iPhone X with iTunes require iTunes 12.7.3. Certain features, including Face ID, may not work as expected when using older version of iTunes. (36546243)

Messages in iCloud

iOS 11.3 beta includes Messages in iCloud for testing and evaluation purposes. Messages will prompt users to turn on Messages in iCloud on first launch after upgrading to iOS 11.3 beta. Please note that Messages in iCloud is automatically enabled for users who have two-factor authentication and iCloud Backup enabled.

USB

To improve security, for a locked iOS device to communicate with USB accessories you must either connect an accessory via lightning connector to the device while unlocked or enter your device passcode while connected, at least once a week.

If you use iAP USB accessories over the Lightning connector (including assistive devices and wired CarPlay) or connect to a Mac/PC, you may therefore need to periodically enter your passcode if you have a passcode set on your iPhone, iPad, or iPod Touch.