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You can manage & track your card collection and decks once you create an account and login.
It can refer to your sideboard, however your outside the game cards do not have to be in your sideboard to be considered detectable by the game.
In resolving the Brainstorm, you will play both Defensive Formations. Skywarps ability will trigger for each of them, but you wont draw cards for the ability until youve finished resolving the Brainstorm. Later rules for competitive play required "outside the game" battle cards to be in your sideboard.