At startup, insert the CD and immediately hold down the 'C' key until the appearance of the selection screen.

Yes, this is possible by following the instructions below:

- Copy the ISO image to the USB stick

- Copy the boot.img from the ISO image (contained in the directory mac_pp32/) and copy it at the root of the usb stick

- Boot from usb stick by typing from OpenFirmware:

boot / pci @ 1b @ f2000000/usb, 1/disk @ 1:, bi = boot.img usbscsi0: morpho-2.5.iso (usb@1b,1/1/disk@1 may vary depending on the port where you connect the USB stick, the command dev / ls can tell you exactly). (for Fab)

You can find a tutorial on the following link : http://www.sterpin.net/ddMacMini.htm