There's no ROM version supported by MAME that I know of that gives a single player the secret doors even when they have died unless they are using the Original Game cheat code. I've tried all of them from Japan v0.0 onwards. "Original Game" does suggest that there might be some prototype version that did so. USA v5.1 is the one with the Super Game selection screen, other versions don't have it. By the way, I have an original Romstar Bubble Bobble PCB running USA version 1.0.

It was my understanding also that only 1 player has to survive in a 2 player game for the doors to appear.

I just started trying to speedrun the game and I got a 38:46 but I just found your video guide and I realised that it could be done much better.