Apple released two beta version of iOS 12. Eleventh for developers and ninth for public testers.
Fresh firmware was released only four days after the release of previous versions.
To install the test version for developers, you need to go to the Apple Developer website and download the appropriate profile. To install the public test firmware you can go to the Apple Beta Program, download the profile to the system and reboot the device.
Both have the same firmware build number. This means that it is the same software. Usually, Apple offers a more advanced software for those who develops applications.
While no significant changes introduced in iOS 12 beta 11 was found. Probably Apple engineers continue to fix bugs and to prepare the system for global release in September 2018.