Odeers may be more appropriate here than ideers? I just tried booting an iMac CRT 500MHz (Summer 2001) running 10.4.9 with SecUpdate 2007-05 from:
iMac Install OS 9.0 Z691-2464-A
iMac Install OS 9.0.4 Z691-2629-A
Full Install OS 9.1 Z691-2748-A
which were all totally ignored, with either c key or option key held at startup. However, Full Install OS 9.2.1 Z691-3334-A enabled booting to the Installer desktop. This accords with the behaviour that I noticed when setting up four CRT 500MHz iMacs from 9.1. I could partition the drives and install OS 9 disk drivers, but after installation of OS 9.2.2 and OS 10.3.x or 10.4.x, OS 9.1 would not boot any of them.
I have to believe that this is deliberate on Apple's part, since OS 9.1 is not a happy exponent of Classic Mode. I marvel that you were able to boot from OS 9.0.4 but not from 9.2.x. Missing OS 9 drivers does not seem to be an explanation, because the Mac boots from 9.0.4. You could look and guess for ever-and-a-day and get no resolution. Perhaps it is worth your while to back up your drive, reformat (and re-partition) as you wish, and be sure to install the latest OS 9 disk drivers from 9.2.1 or in Disk Utility under OS 10.4.
de
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(60x) 13DT + 3PB + PTPro; (G3) 7DT/MT; (G4) 3T + PB. System 8.1 to OS 10.5.8
iMac Install OS 9.0 Z691-2464-A
iMac Install OS 9.0.4 Z691-2629-A
Full Install OS 9.1 Z691-2748-A
which were all totally ignored, with either c key or option key held at startup. However, Full Install OS 9.2.1 Z691-3334-A enabled booting to the Installer desktop. This accords with the behaviour that I noticed when setting up four CRT 500MHz iMacs from 9.1. I could partition the drives and install OS 9 disk drivers, but after installation of OS 9.2.2 and OS 10.3.x or 10.4.x, OS 9.1 would not boot any of them.
I have to believe that this is deliberate on Apple's part, since OS 9.1 is not a happy exponent of Classic Mode. I marvel that you were able to boot from OS 9.0.4 but not from 9.2.x. Missing OS 9 drivers does not seem to be an explanation, because the Mac boots from 9.0.4. You could look and guess for ever-and-a-day and get no resolution. Perhaps it is worth your while to back up your drive, reformat (and re-partition) as you wish, and be sure to install the latest OS 9 disk drivers from 9.2.1 or in Disk Utility under OS 10.4.
de
_________________
(60x) 13DT + 3PB + PTPro; (G3) 7DT/MT; (G4) 3T + PB. System 8.1 to OS 10.5.8