You’ll need to identify which model G4 you have and then have a look here: https://everymac.com/systems/by-capability/macs-with-secondary-display-support-dual-mirroring.html
You’ll need to identify which model G4 you have and then have a look here: https://everymac.com/systems/by-capability/macs-with-secondary-display-support-dual-mirroring.html