thank you for finding this 👍
I'm not sure how this happened: you have custom map completed screen
as the background of the level select screen which shouldn't happen 🤔
(the jack-o lantern just means the model was not found - these pumpkins are the default model
also the white texture means the texture was not found)
anyway if I understand correctly:
you played through the main game and the cut maps and this broke the level select? 🤔
also to answer your question: you get the same secrets on all difficulties
you got an achievement for beating the game on every difficulty but this
didn't went well because higher didn't unlock the lower ones
I kind of misunderstood why people want achievements 😓