It pains me to give this such a low score considering it's meant to be a submission to showcase and boost Ruffle (which is awesome in that regard), but unfortunately as a game it struck me as poorly tagged, designed, and presented. Clicking the Flash Forward badge at the start also made me unable to press the play button, forcing me to restart.
If you really wanted this to be presented as a user sandbox, it should definitely have been more straightforward and honest about it. Maybe the player could have started in a hallway with doors and could pick/enter any of the adventures within, maybe the first adventure (the one you've made) could have forced the player to interact with a "game-like" anomaly to get out of the cell, thus properly introducing the concept, but it just doesn't do any of that.
The "4th wall metagame commands" is something that just gets thrown at the player, completely for free, making it confusing at best, frustrating at worst. You penalize any sort of immersion the player managed to achieve in the first segment by forcing them to suddenly start using meta logic when it wasn't needed before. The game is straight up dishonest, as sometimes there are things you can look at that aren't listed (like the ceiling and floor on the cell), so I stopped playing.
An imp asking for an apple in a forest does not make it sound like I have to open a cheats menu, it should have been something more absurd to force the player to reevaluate what is being demanded of them.
The Red Demon "riddle" is some of the worst designed puzzles I've ever encountered in a text based adventure, specially since "sayonara" is a butchered informal term from the US; it's not even pronounced the way the solution infers. If the demon had said "THEY always say goodbye" it would have made a slight bit of sense, but again you're penalized if you pay attention to the game. The whole thing falls apart from the courtyard on, and it really feels like trying to play along with an 8-year-old storyteller that is bored, rather than trying to enjoy a game designed by someone who wanted me to have a good time and be invested in their work.
Sorry if I dragged on with this, but it legitimately pains me to watch how much of a missed opportunity this was. It's simply beyond me how it ended up the way it is, taking the goals you had in mind (embracing user content, boosting Ruffle, making an adventure). The engine seems to work, but everything else honestly baffled me. Keeping it basic and accessible would have made this a much larger contribution, but it went batshit for really no reason, driving its purpose straight off a cliff instead.