Excellent questions, although some of them may have no answers. Left to the void of the unknown and the mysteries of how exactly the anatomy of something that looks like a child's drawing come to life actually works.

"Oh, it's not uncommon for the name to be given to pet dogs these days." It is dawning on him that if this young man is from the same world as Zagreus, and if he is truly speaking of the actual Cerberus, then he must be talking to a...

"Oh, how rude of me, I haven't properly introduced myself." He extends a hand in greeting. "Aziraphale. And your name...?"