How to cancel Apple's 6splus dual authentication?

According to the official information provided by Apple, only devices that meet the following conditions can open dual authentication:

-iPhone, iPad or iPod touch with iOS9.

-Mac with OS X El Capitan and iTunes 12.3.

-Apple watch with watchOS2.

-Apple TV with tvOS (4th generation)

-Windows PC with iCloud(Windows version) v.5 and iTunes 12.3.

On the iPhone, you can see the option of setting two-factor authentication through the path of "Settings -iCloud- Password and Security". Next, let's take a look at the specific steps.

1. Click "Set Double Authentication" at the bottom of the "Password and Account Security" interface.

2. Click Continue.

3. The prompt shown above appears because your current Apple ID has been logged into other devices that are not iOS9 system. Just click "Open anyway".

4. If there is no credit card bound to the current Apple ID, just click "Open it anyway".

5. Add your current mobile phone number.

6. Enter the received SMS verification code.

After the above six steps, the double authentication has been successfully started, and it can also be cancelled by this method.