To do this, you must have already viewed the staff credits at least once. To view the credits again, press Up, Up, Down, Down, Left, Right, Left, Right, B, A at the selection menu.
Certain duelists have extra requirements to unlock. You must constantly meet these requirements, or they will vanish from the selection screen. If you defeat a duelist with special requirements ten times, they will be permanently selectable, regardless of their past requirements. For example, if you beat Jounouchi ten times, you can then duel him even if you have a Jinzo card in your deck. Losses and ties don't count against your total wins.
Spirit Reaper's effect states that it cannot be destroyed as a result of battle, making it a perfect shield, but if it is targeted by a magic, trap, or monster effect card, then it is destroyed immediately (this includes equip magic cards such as United We Stand or Axe of Despair). However, if you use an equip card on Spirit Reaper, the equip magic card will be destroyed, but Spirit Reaper will remain on the field.Spirit Reaper's effect states that it cannot be destroyed as a result of battle, making it a perfect shield, but if it is targeted by a magic, trap, or monster effect card, then it is destroyed immediately (this includes equip magic cards such as United We Stand or Axe of Despair). However, if you use an equip card on Spirit Reaper, the equip magic card will be destroyed, but Spirit Reaper will remain on the field.
Volt Girl is a powerful 1900 ATK Light element monster that is immediately destroyed if you have a non-Light element monster face-up on your side of the field. However, if you use Snatch Steal to take a non-Light monster from your opponent, it doesn't count as a monster on your side of the field, and therefore Volt Girl lives. This doesn't work with Change of Heart.
To unlock the limitation option, get 100% completion by collecting every single card in the game. Now you can choose to have restricted cards to be no longer restricted.