Not sure about old dogs, but you can definitely teach Addy some new tricks

• If you ask her "How big is Addy?" she puts both hands up over her head.  Then she grabs her hair, but she does the "So big" part just perfectly.
• High 5.
• If you ask her "Where is Addy?" she'll pat herself on the chest.
• Lots of words (usually with the correct meaning): cup, cat, book, door, Mama, Dada, call, phone, car, go, bob-bob (bottle), dipe-dipe (diaper).  Mama and Dada are special words, though, because she only says them when we aren't in the room and she's looking for us.  She also says "oooh-eeee" as an exclamation.  Yes, it's even cuter than you're imagining.
• Nodding yes and no.
• I've been trying to do simple signs with her to help with her gag reflex.  My theory is that she has some anxiety because she isn't sure what we're trying to stuff in her mouth, she isn't ready for more food yet, she's full, etc.  I mostly use ready, eat, cup, drink, mommy, daddy, more, apple, and all done.  Which ones has she picked up on?  "All done" and occasionally "more."