How does another device notify the original device when it changes its password?

  ios, question

Now one device has logged in automatically, and then I retreated to the background. I changed my password in another device.
What I want to know now is how do I know the password has been changed when my current device enters again?
How else can only one account be logged into one device at a time?

This is the logic of the backstage. The backstage verifies the token. Every time you take the token to the backstage verification, the backstage will tell you the current status. The details can be discussed with the backstage partners. You can also make a notification. Is it too late to wait to enter the program again?