For definition purposes:
Two-factor authentication for Apple ID - Two-factor authentication for Apple Account - Apple Support - "A trusted device is an iPhone, iPad, Apple Watch, Apple Vision Pro, or Mac that you’ve already signed in to using two-factor authentication. It’s a device that we know is yours and that can be used to verify your identity by displaying a verification code from Apple when you sign in on a different device or browser."
“Two-factor authentication requires iOS 9 or later, OS X El Capitan or later, or iCloud for Windows 5 or later.”
To see how to get a verification code and sign in with two-factor authentication' click here --> Get a verification code and sign in with two-factor authentication - Apple Support
If you have a trusted device running iOS 9 and later, OS X El Capitan and later, iPadOS 13 and later, or watchOS 6 and later, the verification code is displayed automatically on your trusted devices.
- Use a Trusted Device: Mac, iPhone, iPad, Watch. Code is either generated automatically or manually using Settings on the Trusted Device.
- Text or phone call to a trusted telephone number (any telephone; even landlines).
- Get a code from an Account Recovery Contact --> Set up an account recovery contact - Apple Support
- Instructions at the end about what to do if you cannot get a code and need to use account recovery.
If you lack a way to view a verification code but can still log into your Apple Account, you can add a way to get a code. "You can manage your trusted phone numbers, trusted devices, and other account information from your Apple ID account page." Click here --> https://account.apple.com/
From: Two-factor authentication for Apple Account - Apple Support
If you have no available trusted devices or numbers, and cannot sign into your account (such as when you have a forgotten password) to add a way to get a verification code, read:
How to use account recovery when you can’t reset your Apple ID password - How to use account recovery when you can’t reset your Apple Account password - Apple Support
"The fastest and easiest way to reset your password is from an Apple device. Before you start the account recovery waiting period, try to reset your forgotten password on a trusted device. Or borrow a friend or family member’s iPhone, iPad, or iPod touch and use the Find My iPhone app to reset your password. You can even visit an Apple Store and ask to use a device on site."
If you still need help this page provides country-specific Apple Support contact information ➞ Contact Apple Support - Apple Support