How can I unlock a frozen iPhone 16 Pro during iOS update transfer?

Follow the directions in this link --> Force restart iPhone - Apple Support (CA)

Note: For the last step which is to hold the side power button until you see the Apple Logo, HOLD IT for however long it may take.

Try a Forced Restart on the phone.

Follow the instructions very carefully, as this is a bit tricky. (Hint.....ignore the "off slider" when it appears and keep holding the Side button in until the Apple logo appears, then release the Side button. This might take another 10-20 seconds.)

Force restart iPhone - Apple Support

If still no luck, you will need to contact Apple Support

Support

cfi1598 wrote:

Still will not shut down after following Force Restart or allow login!

You're not trying to shut your phone down, you're trying to get it going again. If in the Forced Restart procedure you tried to use the slider to power off, we advised to NOT do that.

This is a Forced Restart (follow this exactly)

• Press and quickly release the volume up button.
• Then immediate press and quickly the volume down button.
• Then press and KEEP HOLDING the side power button. KEEP HOLDING it, even if you see the slide to power off option and KEEP HOLDING it until you see the Apple Logo. This could take anywhere from 10 - 30 seconds. Once you see the Apple Logo, release the side power button.