You need to maintain state related to which is user's own version of website and which is not.

This state needs to be accessible to all versions of your apps.

As far as my knowledge goes, it is not possible without a central medium. You can either maintain it in a remote server or in a master_domain cookie, to which all apps can redirect, to read current state(similar to SSO).

The second approach is not that clean and you would still need a central server, I would prefer first approach only.

Sharing states/cookies across domains is not supported by browsers due to security concerns. So doing it completely in browser is not possible at moment.