Have you played Rogue Legacy? It's like Spelunky in that it's a 2D-platformer which prices itself in being unforgiving, but also there are four specific bosses you need to beat (functionally equivalent to your high-level design, really) prior to fighting a final boss then "escaping". You might consider giving it a go for your research.
Thanks I have heard of it but never really have played it. I'm now just looking into this game and is definitely has a similar concept! I will give this game a go and really see how it plays out. Thank you for the recommendation