1. Decks are not fixed. You can change your deck against different opponents.
2. All matches will be best of 5 duels. You cannot change your deck in between the duels.
3. You may request your opponent to have best of 3 instead, if you're pressed for time. However, this can happen only if both players agree to it BEFORE starting any duels. You will NOT be allowed to change it back to best of 5 after a match has started.