Hi, Roulette -
I don't understand why that model specific thing happens. I mean, what do they expect you to do if you need to or want to go backwards to a specific OS ?
In general, no Mac can use an OS earlier (older) than the one that model first shipped with (this is not something new; it's been that way for a long, long time). The reason for that is that the hardware on a machine requires compatible OS components in order for the OS to run the machine. An OS older than the one that first shipped with a machine won't have the necessary components or coding needed by some of the hardware (the logic board, for example) on the machine, hardware whose needs were not known at the time the OS was designed.
As far as model-specific versions go, that generally results from a model being designed and released after the retail (commercial) release of an OS, but before the release of the next OS version. In order to run the newer hardware, the OS is modified (parts of it rewritten) in order to be compatible with the newer hardware. I guess that practice should result in a minor version number change - OS 8.6.2, for example - but that wasn't done.
There are soetimes some indicators of the changes. For example, the G4 (DA) models ostensibly shipped with OS 9.1. However, it is a model-specific version, and that G4 can not use a retail OS 9.1 Install CD (I iknow - I tried), which has Finder v. 9.1. Why they didn't call it OS 9.1.1, I don't know.
I really don't have to go to 8.6 exactly, I could run 8.anything really. So would that work ?
On the G4 (AGP)? No. It can not use any OS earlier than the model-specific version of OS 8.6 that first shipped with it. That means no OS 8.5, 8.1, 7.6, etc.
I know I could go to System 6, 7, or even a earlier 8...
Not on any G4.
Like Firewire drives, CD burning...
CD burning is possible on most any Mac with a built-in CD drive. However, firewire is a different thing. Firewire is not built-in on any Mac whose original OS was earlier than OS 8.6; as far as I know, the extensions needed for firewire do not come with any earlier OS version.
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It only runs on System 6, System 7, and OS 8.x.
I googled the "SP12 Librarian" software, and found this webpage which is pretty informative -
http://www.watersedgesoftware.com/05Solutions/SP-12Librarian/index.html
That page does state, under System Requirements -
System 6, System 7, or Mac OS 8.x is required on your Macintosh. SP-12 Librarian does not support Mac OS 9 or newer.
So, OS 9 is out.
It also states -
Your Macintosh must have the built-in "classic" (AKA "standard") Modem and Printer serial ports.
Further reading indicates those ports will be used for cable connections to an external MIDI interface.
No G4 has built-in serial ports. You can find adapters for USB-to-serial ports, and perhaps PCI cards to provide them. However, that webpage is so specific about needs, that I would tend to respect the term "built-in".
It sounds like you should look for a different machine.
I though at first that a Blue & White G3 might fill the need, specifically re the OS issue, but that model, too, does not have built-in serial ports.
A G3 Beige/Platinum model, either a G3 MiniTower (MT), Desktop (DT), or All-in-one (AIO), would fill their requirements nicely. All three models originally came with OS 8.0, so can use a retail OS 8.1, 8.5, 8.5.1, or 8.6 Install CD; and all three have built-in serial ports. The fastest is the G3 MT 333MHz model; the G3 MT also has the largest power supply of the three models.
The downside is that none of those G3s have built-in firewire, nor USB for that matter. I'm pretty sure you can add USB to them via a PCI card; I don't know about firewire.
There are some pretty savvy folk who hang out in the G3 forum, who should be able to answer questions about adding firewire to the Beige/Platinum models.