It's definitely possible to use the spawn at start function to create triggers and audio zones in your game, and it sounds like you have a good idea for using video and image zones to enhance the player's experience.
To create a video or image zone that only appears after the player has found the bolt cutters and is returning to the gate, you could use a trigger zone to activate the video or image zone at the appropriate time. Here's an example of how you could set this up in your game:
Create a trigger zone that is placed after the gate, but before the area where the bolt cutters are found.
Inside the trigger zone's on trigger enter function, use the spawn command to create the video or image zone at the gate location.
Set the video or image zone's visibility to false when it is spawned, so that it doesn't appear until the trigger zone is activated.
When the player returns to the gate with the bolt cutters, they will trigger the trigger zone, which will then make the video or image zone visible.
This approach allows you to control when the video or image zone appears and ensure that it is only shown at the appropriate time in the game. Let me know if you have any further questions or need help implementing this in your game.