Subrule · Chapter 9
cr:9.1.3b
If a flip-card is inside the game, its front-face is active until a rule or effect would make its back-face active. If the card would then become a new card, its front-face is active again.[3.0.9]
Example: Construct Nitro Mechanoid is the front-face of a flip-card. When it resolves on the stack, its Construct subtype rules that it enters the arena with its back face active, turning it into Nitro Mechanoid. If it is destroyed and moves to the graveyard, it becomes a Construct Nitro Mechanoid again because its front-face is active.