Decks from any format (e.g., Standard, Expanded, etc.) can be played, but note that success in the game is based on overall damage output, so you may deal more damage, and thus have more success with newer cards (i.e., Sword and Shield onwards)
This was a huge problem with the black cards, as those commonly saw themes related to death and bloodshed
It's in the Naya (red, white, green) MTG color combination, and its face commander is Dogmeat
Some cards have a version name listed under them, like Stitch - Covert Agent. Ink: The color band and symbol underneath the cards name shows its ink type
There are also cards that let you gain mana rapidly even early in the game, or rifle through your deck to select a specific card, or still other special powers that compound the power of the awful beast youre chained to