Re: dogs cannot become cats
A few hundred more generations with the right selection criteria and this breed could easily become much more cat-like. The pictured example already has more cat-like chest musculature and a shorter snout than my dog. Granted the dog will still be a dog and not a cat but the traits will be fairly similar.
A good example is the ancestors or modern monkeys, the same ones that lead to humans like you, that followed an evolutionary path to become bird-like. Despite being able to fly and have very light-weight bone structures bats are not birds.