Dogs aren’t a playable race so they can’t have class levels. But there is no rule saying dogs can’t learn languages. And they can be Sidekicks, but that’s more a rule specifically designed to allow them to play. There’s also no rule saying they can’t wield weapons. One-handed and two-handed weapons both require hands to use, but there aren’t actually any weapons listed as one-handed.
There’s no rule saying a dog can’t play!
Dogs aren’t a playable race so they can’t have class levels. But there is no rule saying dogs can’t learn languages. And they can be Sidekicks, but that’s more a rule specifically designed to allow them to play. There’s also no rule saying they can’t wield weapons. One-handed and two-handed weapons both require hands to use, but there aren’t actually any weapons listed as one-handed.