Rosetta 2 is not installed by default, you are prompted to install it for the first run of an x64 app - but only in the gui.
If you run an x64 app from the command line, directly or prefixed with arch -arch x86_64, it will simply fail. You have to double-click an x64 .app bundle in the Finder to trigger the "Would you like to install Rosetta?" popup.
Is there any way/API available to launch intel app/binary via terminal/NStask so that OS can show popup instead of launch failing. If not, any cmd available to show rosetta pop?