yalesky:

Can I turn off two-factor authentication ?
If you already use two-factor authentication, you can no longer turn it off. Certain features in the latest versions of iOS and macOS require this extra level of security, which is designed to protect your information. If you recently updated your account, you can unenroll for two weeks. Just open your enrollment confirmation email and click the link to return to your previous security settings. Keep in mind, this makes your account less secure and means that you can't use features that require higher security.
Is this different than Apple’s current two-step verification feature?

Yes. Two-factor authentication is built directly into iOS, macOS, tvOS, watchOS, and Apple’s web sites. It uses different methods to trust devices and deliver verification codes, and offers a more streamlined user experience. You need two-factor authentication to use certain features that require improved security.

The older two-step verification feature continues to work separately for users who are already enrolled.

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Published Date: August 21, 2019