I've noticed sometimes AI opponents play as if they are aware of the contents of your hand. I'll often find they wait until you use up all of your move cards before they cast terrain effects (I'm aware one is always visable, but sometimes more than one is drawn), and the opposite also applies where the AI will save move cards and avoid using them if there happens to be a terrain effect in my own hand. Are AI opponents always aware of the contents of the players hand?
Unless there's some mad conspiracy going around . . . no, Gary can't see anything unrevealed. I mean, come on, any videogame that let the computer cheat like that would be pretty unwelcome. If you check discussion over here, you'll see we've found Gary is strongly limited by what he can see: he won't use an Armor-removing Attack if he is unaware you hold Armor, to the point of refusing to use his Attacks completely. And losing.
