Hey, thanks for the feedback. You should be able to approach the fairies after learning invisibility and mana drain. Invisibility is learnt through the story and you definitely have it by now. Mana drain from Magda.Not sure if it's mentioned in the hint, but definitely in the dialogue before you approach them, at least the first time.
I agree there isn't much content in the Underworld yet - it is work in progress. The ghost queue can be finished in 0.50. The teddy bear is optional and isn't supposed to be found that easily. More sandbox improvements will be coming after update 0.50.
Trying to go west past the maze brings you back, as you need to complete the maze first. This is already available in patch 0.50 which will be releasing soon. It has nothing to do with battle minigame being on or off. I'll look into hinting this progression block later. The minigame being off does indeed simply bypass fights.
Difficulties with entering points of interest like the church have been somewhat improved in 0.50. Unless you mean the large locations as well, but I haven't seen any issues there. The trigger zones are quite big.
As for the last issue, are you talking about the corpses number? These definitely don't wake you up from the underworld. Can you provide a screenshot?