Hello!
I've been wanting to beat this game on the real system (already done it on emulators) but it just doesn't let me get through when I play. Using some items just kills the game for whatever reason, and one of them happens to be using the item that's meant to save Denzel so the game can't be completed at least on my set up (OG NES, NTSC edition, through an Everdrive so perhaps some kind of weird compatibility issue, but all the other Codemasters games work without a hitch, including the other unreleased Dizzy as far as I can tell.) I've noticed that what kills the game differs by language - it freezes up MUCH earlier in German. In English the two items I can't use are the aforementioned to save Denzel and the Game Genie lamp.
* Edit, here's a video. It isn't using the item to save Denzel, I can't get that far. The initial dialog box with Denzel is what stops the game. https://youtu.be/McYbAiRfv0U