Hi I'm Saltyjustice, and I did the coding work for Megamare-X. This is v121a which is the last internal version we made.
I don't think it was ever demo'd to the public, earlier versions were. Here are some important diagnostics keys because
without them you won't be getting very far.

The most important key is the I key. Press it during normal play to bring up the debug menu. This menu lets you toggle
a lot of things and visit the level select. The level select has all of the stages at various levels of completion, including
debug stages to test things like item pickups. You can also see the proper level select and world map this way.

Lyra starts the game without the "Protosuit", which means she can't charge and can't walljump. When you reach the red girder
part of the level you can't proceed without it and the cutscene where you get it in the bombed out lab does not fire. Use
the debug menu to get it and climb up. The rest of the stage should work including the boss battle and cutscene.

You can use the F1 to F10 keys to jump around the map to preset spots. F11 toggles fullscreen, F12 shows collision zones.
The p key damages Lyra.
The o key kills Lyra (how could you?)

In this version the map layered incorrectly during the Chrysalis fight