how much can I do to my G5 ppc 10.4.11?

I have a G5 ppc running on 10.11.
I'm finding out that the system is high as it can go? 10.5 Leopard isn't supported?
Also does anyone know if I can take hard drive out of the G4 ppc and switch the pin to slave it and put it in the G5 ppc and access files and programs from it?

10.5 Leopard does support the PowerPC processor..however that's the last version that will support it..

Regards

Thank you so much

And the hard drive is a no go......G4's use IDE drives and G5 SATA. You could pop the IDE drive in an external case and hook up by Firewire to the G5.

If transfer speed from the G4's ATA drive isn't an issue, a cheap way to hook it to your G5 is via a USB adaptor kit, like this Amazon.com: Sabrent USB-DSC5 Serial ATA or IDE 2.5-/3.5-Inch to USB 2.0 Cable Converter Adapter with Power Supply: Electronics: Reviews, Prices & more.