I have got an old PowerBook G4 with FireWire 400, and a new(ish) iMac with FireWire 800.
If I want to start the PowerBook G4 in Target mode, I can't plug it into my iMac because they use different FireWire. I am not going to spend any money on a FireWire 400 -> 800 cable, or a FireWire 400 -> USB cable. Target mode does not work with USB, only FireWire.
I have got an old Maxtor (now Seagate) One Touch FireWire 400 and USB external hard drive (I think this might be it). Could I plug the FireWire 400 coming from my PowerBook into the Maxtor, and the USB coming from the Maxtor into the iMac - and get the data from the PowerBook G4 in Target Mode going into the iMac?