After 'obtaining' 9.0.4 International English, I did some testing VS different ROMs.
Tests with no mounted disk image, just the CD, set to boot from 9.0.4 CD.
Old World ROM = completes boot from the CD.
(I didn't try installing 9.0.4 with the Old World ROM.)
New World iMac ROM = completes boot from the CD.
New World ROM from ROM Update 1.0 = boots from CD until extensions begin to load then dies.
Tests with an HFV mounted, set to boot from 9.0.4 CD.
Old World ROM with HFV with 8.1 installed = completes boot from the CD.
New World iMac ROM with HFV with 8.1 installed = does the splash and die just like it does trying to boot from any 8.0 or 8.1 with this ROM.
Apparently it will not boot from CD with that New World ROM if any mounted volume has a blessed 8.0/8.1 System Folder, even when it's set to boot from a CD. It starts the boot from the CD, so why does it crash??? Tried this one a few times to be sure it wasn't a random crash.
New World iMac ROM with HFV that has 9.0.4 and HFV that has 8.1 (bootable with Old World ROM) both mounted. Boots from 9.0.4 and *doesn't die!* It didn't do any weirdness like un-blessing the 8.1 System Folder.
Same as above, Old World, put the 8.1 HFV first in the list and it boots normally. Would be nice to just be able to select which disk image to boot from or at least have up/down buttons to shift the boot one to the top.
Shall I repeat these tests using an 8.6 CD?
P.S. It won't copy and paste icons from Get Info on hard drives.

Basilisk II can.