Important: From the online Read Me file:
"You can install this version of Mac OS 9.2 on any of the following computers: Power Mac G4, Power Macintosh G3, PowerBook G4, PowerBook G3 (except the original PowerBook G3), iMac, and iBook."
In other words, OS 9.2.1 can only be installed on machines that are capable of supporting OS X. The Read Me contains no information detailing what's been changed, other than offering "improved Classic compatability."

