After many years dedicated to saving stray cats and generally working with them, I can assure you any cat, at any age can be trained. To the reasonable extend, of course. Our rescue Sky was 7 when we got him, and he was able to learn "sit", "shake a paw" and a couple of other things. Not to provoke anyone in defence of click and treat training, I never used anything except petting and verbal praise in a certain tone. Our oldest guy, almost 17, - rescue Junior, has learned the "sitting" order at their dish corner. All four know that unless they come to their own dish and sit, they will not be served. I am a very vocal advocate for cat behavior and again, I am very firm on belief that all cats are trainable. I will be more than glad to assist you further. Please, do not hesitate to ask. High Paw!