Expert is pretty nuts. There’s an old guide on the internet with walkthroughs for the first three difficulties and a partial guide to expert because the author got stuck and couldn’t finish. There’s also a more complete guide that someone made by looking at the ROM to figure out what exactly you need to do to reveal each secret. So far I haven’t used either for expert, though I used the former for the one thing I was stuck on in beginner and the latter for what I was stuck on in average. I’m hoping but by no means confident I’ll be able to get expert on my own. I’m playing with infinite lives turned on and enemies turned off, and it’s hard to imagine how anyone could beat the game without those two changes.
Unfortunately I don’t have a picture of my map to hand but I’ve moved to an emulator on PC and have stitched my map together out of screenshots. To those screenshots I’ve added secrets as I reveal them along with what I did to reveal them (usually either collecting something, dropping some tiles, or striking particular tiles repeatedly). I’ve been pretty thorough about trying all my methods to reveal things, so it’s pretty slow. Even so I might have missed stuff - in at least one room dropping all the tiles at once didn’t reveal a secret but just dropping the middle section did, and I can’t be sure I haven’t missed more of those. My map might also be incomplete because I wasn’t bothering to record secret reveals that only gave treasure, and I’ve since realised that some of those treasures might have revealed other secrets on different screens. For the first half to three quarters of the map it seemed like every secret directly connected - I dropped a tile and a treasure appeared, then I picked up that treasure and a key appeared. Then I hit a room in which dropping all the tiles made a blank tile appear, which I had not seen before. I brought back the tiles and walked over the one that appeared and a sound played. What did it do? Hard to say, but I’ve since noticed a bunch of treasures that weren’t previously there in rooms I’ve already visited. I suspect walking on that blank tile either made those all appear or it made one of them appear, and collecting it made the next appear, and so on. On my map these are all marked with question marks. I also found a room with like six or seven keys all in a row, none of which opened any doors in that room. I’m hoping they’ve opened doors to some of the areas I haven’t been able to reach yet.