Come to think of it Giro has a forehead marking and turned into a cyber elf when he died, so he's probably a reploid to begin with, and thus wouldn't show his age anyway.
There's no "probably" about it, Giro *IS* a Reploid.
However, the fact that he turns into a cyber-elf does not factor into that. Machine-body humans can go the same way, as Hurricaune has both humans and Reploids imprisoned for her cyber-elf production.
Who knows, it's possible that Ciel BUILT Giro. It would explain his resemblance to Zero and why he's compatible with Model Z.
Possible. But I think Prairie would probably refer to Giro as family if that were the case.
Usage of Model Z is irrelevant to that, though. ALL Biometal compatibility is determined by Albert (save Ashe who was unexpected). Ciel didn't understand enough of the R.O.C.K. System to modify that aspect of it.
I don't know, Prairie made it sound like the order was addressed to Giro specifically:
"Calm down Aile! I don't know much about what's going on either. The one that gave Giro the order to protect you was the first commander."
Turn it around: You could also say that the order is addressing Aile specifically. But we know that's not the case; Giro's disk profile lists him as caring for multiple children.
She speaks of Giro and Aile because it's what Aile is asking about. The other Guardians, and the other children, are irrelevant to the discussion. That's all.