If Madotsuki's only game is NASU, why is there an entire area of her mind paying homage to MOTHER? I mean, if she played and liked a game about love and friendship that much, Yume Nikki would have a different ending...
Or maybe it ended that way because she realized she didn't have anything like that.
Let's not forget, Mother and EarthBound certainly have dark sides to their stories too. Most people focus on the uplifting message of hope and friendship, but another side of the story certainly exists. In fact, Itoi likened Earthbound to a prostitute in an interview that he gave on the subject, and there are a lot of articles out there which deconstruct it and show how seriously messed up a lot of the stuff in the series really is.
As for why NASU is her only game, perhaps the circumstances that led to her current situation involved losing some or a lot of her possessions. It could be anything, really.
Where do the stairs come from? They only are there when the effects are in the Nexus, and if you take them out, the stairs actually disappear. And why do Jellyfish appear near Madotsuki's blood!?
This is more of a WMG but, maybe it was All Just a Dream, "non dream" sequences included.
Alternatively: the stairs are always there, but they're not visible at first in order to make it more obvious for the player what happens next. The in-universe explanation could be that Madotsuki's just not acknowledging them.
As for the Jellyfish I personally don't think they're literally there. They're just credits decoration, maybe with meaning or maybe not, but I don't think they're actually present physically.
Why is it the general consensus that Uboa is male? I think it looks pretty female (judging by the hair). Either way, how would we even know what gender Uboa is?
People tend to refer to entities of ambiguous gender as "he" by default.
Although it's much better to use "they/them" for genderless/unknown gender...er...beings. Or maybe just "it" considering we don't even know if Uboa is sentient.
Nobody talks much about the Lamp World. It's kind of a dead end, after you get the Lamp effect there's nowhere to go except a dead end door. But because of that nobody seems to have noticed that the structure the go-nowhere-door is attached to has a walled-off room in it, with some sort of bright red thing on the ground. I've seen (and heard about) quite a few well-buried secrets in the game, but nobody mentions this inaccessible room and item. What on earth IS that thing? And why do I seem to be the only one painfully curious about it?
I'm pretty sure that's one of the spots a Toriningen can teleport you to.
You're thinking of the あ room in the Number World proper. The walled-off room the other troper is speaking of is easily seen in the Number World-like building at the bottom of this pic◊. To my knowledge, no Toriningen teleports you there, though it could be reserved for the Lunatic Toriningen permanently trapped behind the counter in the City.
I think that it's the spot with the eye-shaped tile. If you get teleported in there and step on it, it replaces the transparent floor and scrolling background with the same tile you step on, making the area less disorienting. But unless you have an Effect that lets you return to the Nexus, it's useless.
Is Kikiyama still alive? By that, I mean is he still actively working on this game because I vaguely remember him saying that it's far from complete.
The game hasn't been updated in quite some time, but yes. Kikiyama is still alive.
Also, "he" is generally agreed to be a "she."
If Madotsuki's time in the Real World is really her waking life, how on Earth does she stay alive? It's fairly obvious that she at least dreams that she's a biologically normal human being (she can apparently drink health drinks and go to the bathroom in her dreams, and some of the aspects of her dreams are uncomfortably visceral), but she never does anything but sleep, write in her diary, and play NASU. Unless the game takes place over the course of a single night and she's hallucinating the time changes outside, which is far from impossible, she should have died quite awhile before the ending from dehydration.