Hi, melrosepoint -
From the specs you've given it would appear that you have one of the new Intel-processor iMacs. You should be able to confirm that in System Profile - not sure where that's located in OSX, perhaps in the Apple menu.
If that is the case, then you would be able to use only those games which run in OSX.
Earlier Macs, those with a G5 or earlier processor, could use OS 9 as Classic, which provided an environment in which many OS 9 programs could be run. Most G4 and earlier models could also boot into OS 9 (use OS 9 as the Operating System). In all of those cases OS 9, either as a bootable OS or as Classic-only, was installable from the original disk set that came with the machine.
However, Apple does not support Classic for the Intel-processor Macs - and so it is not included with the original disk set for those machines.
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There is a possible work-around. Although Apple does not support the use of OS 9 or Classic with Intel-processor Macs, there is at least one third-party emulator, SheepShaver, which allows the use of OS 9.0.4 on such machines. You can read up on it here -
SheepShaver
Caution - many games insist upon having direct access to the hardware, primarily to the graphics card. Any such program does not fare well, if it runs at all, in Classic; since Classic is OS 9 used as a program while OSX is running the machine, a program run in Classic does not have direct access to the hardware. It is probable that such a program would not do well in SheepShaver either.