My Beau has tried opening our door to the outside. I always lock it behind me so he’s had no success yet, but he clearly understands that pushing down on the handle opens the door, he tried a couple of times.
I think he’s come to understand about keys, too. If we’re heading out and I stand too long at the locked door, he will look pointedly at the key in the lock and then back at me, and if I wait he’ll sometimes nose it and look at me or bark at me. As if he’s telling me to get a move on and make it open, so we can get out of here.