For three weeks Apple actively tested the beta version of iOS 12 on the developers, having managed to submit two versions of the system at once. Finally, a test firmware for all comers was also available.
To be able to install the firmware, you must register with the Apple test program by logging in with Apple ID on the company’s official website .
Then upload the proposed profile to iOS device and install it.
After the installation is complete, the first test version of iOS 12 will appear in the Updates section in the system settings.
Note that the system is still very unstable. Install it on the main device is not recommended, but if you can not wait to try out new chips iOS 12 , you can try. Roll back to a stable iOS 11 is always possible.
Before installing, do not forget to back up all data.