Hi,

It isn't as much a question of whether a rear amp can sit, but more a consideration of what that repeated motion will mean over time.

Chester is a young dog, but as a Tripawd his joints & spine will be stressed more than a quadpaw over the years. I think it's OK to teach the sits and downs, but in short sessions, and not relying on them as a primary behaviors. You might consider teaching stand, stay and wait as your go-to commands.

Because a young dog can perform behaviors or run, twist and jump, doesn't mean they should. I think you have to look at where Chester is going to be as an adult and ultimately a senior dog and limit the wear and tear on his body where you can. Shorter sessions of intense activity, limiting repetitive movements (that you ask for, what he does on his own is fine), etc

It is usually more difficult for a rear amp to go up stairs, rather than down, Going up also puts more stress on their spines...you might want to teach him to wait at the bottom for some help up.. Do you think he just never learned how to walk down stairs in his previous life? It may just be a puppy lesson not learned. My dog is a rear amp, 13, on the lazy side, with arthritis & runs down 27 stairs without help. 

He may be tired on his walks. He is using more energy on three legs, especially this early. He also may not really understand the leash concept yet.....this all can add to his fatigue. Maybe you can try more frequent, shorter walks for now. You may find the Ruff Wear harness , like any harness with a D-ring on the top, may encourage pulling on the leash. You might try a Sensation or Sensible (same manufacturer, different fabrics/pricepoints). Most of the other no-pull harnesses on the market slip & are not nearly as effective.

My dog laid on her amputation side from the night of surgery and quickly learned how to get up from that side.

He's adorable...and I love his name!

Mastering the stay command is not dependent on the position the dog is in prior to "staying". It should always be taught independently of any other behaviors. A dog can be in any position prior to being asked to stay. You particularly don't want to teach it only in association with another specific behavior, such as sit or down. If, at some point you find yourself separated from your dog and his survival depends on his staying put ( if, for example, he runs across a street) you want to be able to respond to the stay command in whatever position he is in. Dogs do not automatically generalize and need to be taught commands in different environments, circumstances, positions and in the face of distractions.

It isn't a matter of him being able to get into any position, but the repetitive up & down movement that takes a toll over time. He will learn all of these behaviors quickly, but it will be up to you to monitor how they are illicited during his lifetime. Some careful protection early, may save you both the pain and expense of arthritis later in life.

A large, often missing piece, of training is attention to the cerebral development. Puzzle type games which require problem solving, nose work, etc can go along way in fostering the appropriate skill sets all dogs need.

Flexi leads are not the best choice for any training exercise. They do not teach leash walking, as they allow a dog to do as he pleases. It is impossible for the handler to have any control if needed, potentially putting your dog at risk. They can be particularly dangerous (especially the line type frequently used for smaller dogs) for a young, rear amp, who hasn't yet developed any leash manners. It is extremely easy for the excess line to get tangled on the remaining back leg & cause serious injury.

Aside from all of the dangers these leads carry in normal situations, allowing your Tripawd (or quadpaw) to interact with other dogs, when any of them are on a flexi lead is an accident waiting to happen.

If you have a mature, dog, with reliable manners, they can work if the handler is diligent, but be sure to use the tape type.