"Gameplay demo" (tentative) is a cutscene in Resident Evil 0.
The scene is not in the Gallery and will only trigger if the player waits approximately 15 seconds on the title menu. The demo shows various situations where Rebecca Chambers and Billy Coen are able to cooperate throughout the game. The trailer also teases the Mimicry Marcus enemy.
The demo appears to be using recorded footage and not scripted gameplay.
After the demo is finished playing, the title movie plays immediately after. After approximately 15 more seconds, the two scenes will loop again. This continues until the player selects an option from the title menu.