As for the new version of this push, I haven't found any new features added to iOS 12.4 Beta 7, but it is clear that Apple continues to fix bugs in the new system.

According to the developer, iOS 12.4 should be the last version of iOS 12 system update. Previously, Apple sent the iOS 12.3.1 system, mainly to fix the problem of spam flooding in information applications.

Currently, Apple has officially stopped signing iOS 12.2 code, which means you can't downgrade to this system version.

From the first system screenshot of iOS 13, the new system does include dark mode, and the Dock on the main screen becomes dark. Users want to enable this mode and select it directly in the settings. For this mode, The iPhone of the OLED screen will be more expectant, because it can extend battery life when it is activated.