How do I update my iPhone 8 from iOS 12 to 15?

If you have been keeping your iPhone 8 from doing automatic updates, and it is still on iOS 12, you should be able to update it to the latest version of iOS 16. You might not have much luck doing this wirelessly, and might need to do a manual update with the aid of a Mac or a Windows PC to improve your odds of success.

Since your iPhone 8 can run iOS 16, and iOS 16 has been out for quite a long time, your phone won't offer to let you pick and choose iOS 15, specifically. You will need to update past iOS 15 to iOS 16.

Update your iPhone or iPad - Apple Support

Updating iOS: common issues and solutions - Apple Community

Note that if you have misidentified your iPhone, and this is actually an iPhone 5s, 6, or 6 Plus, it cannot update past iOS 12 and will not offer you the option. For those iPhones, iOS 12 is the end of the line.

"How do I update my iPhone 8 from iOS 12 to 15?: How is it possible to updates the latest Version in iPhone 8with iOS 12 to 15. although it always hang sometimes if I tried updating mine.?"

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Updating an iPhone 8 to iOS15:

A. Is it Compatible?

Yes. It is compatible.

1. Go here: iOS 15 - Apple
2. Scroll to: iOS 15 is compatible with these devices.

B. Disable Screen Time:

If Screen Time is enabled, then it may be restring you from performing the update. So, disable it:

1. Go to: Settings
2. Tap: Screen Time
3. Tap: Turn Off Screen Time(so that it is greyed-out)

C. Update Using a Computer:

Have a Computer Handy? If so, try using a computer to update. Use my User Tip Update your iPhone Using a Computer - User Tip. If any updates are availabe, they will install, sure enough.

"Why is it that iPhone 8 hanging if tried to update new versions?"

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Troubleshooting Losing Calls:

A. Go here: If your Call Fails or you can’t Receive Calls on your iPhone - Apple Support

B. Whom to Contact:

Contact your Carrier, if you are having issues with numbers not being pressed as they should be, and if you are losing calls for no apparent reason.