Installing Safari beta version is apparently only possible by replacing the builtin Safari version. In this case version 11.1.2 with 12. If beta version does not work, gives too much trouble or is just unpleasant:
How do we downgrade to an official stable version, currently Safari 11.1.2 for 10.12.6 Sierra?
I tried to restore everything relating to 11.1.2 from a backup (going by what is found that is in the installer package), I located and re-applied the 11.1.2_Sierra.pkg. Yet Safari now refuses to work entirely.
Crashed Thread: 3 Dispatch queue: com.apple.SafariCore.RemotePlistController.internalQueue Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x0000000000000000, 0x0000000000000000 Exception Note: EXC_CORPSE_NOTIFY Application Specific Information: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[_NSPlaceholderData initWithContentsOfURL:options:error:]: nil URL argument' terminating with uncaught exception of type NSException abort() called
Is there any way around re-installing the entire system?