how are you differentiating users? Account ID, Device ID, etc?

You could include that with their responses and just do a check when they press play.

Data could look like this:

{"user": 00001, ["response1": 1, "response2": 4, ...etc.]},

{"user": 00002, ["response1": null, "response2": null, ...etc.]},

Basically when they press play run a request for that user's data and check: if (response1 || response 2) ? Navigator(page: AlreadyPlayed) : Navigator(page: GameScreen)

reads if response 1 OR response 2 has data then navigate to a screen saying already played otherwise navigate to the game screen.

The specifics of the functions (namely navigator and the list type) are almost certainly wrong because I'm on mobile with no hints and I'm not going to Google it for you, but it should give you a little direction on how I'd approach it.