I've thought about releasing the original draft to the public, yes, but there are a few issues. There's a bit of 4chan edgy humour there which I've since looked back on critically and have come to regret, so I'd need to take time to reread it all from scratch. But since I'd be doing that with the goal of presenting this text, I'd also feel tempted to polish other parts where I was very much rushing things -- at which point a bigger issue becomes apparent.
The truth is that the text of the quest is, itself, incomplete without the context of the threads where I posted them. The input I received, and which was not recorded into the text itself, fills in gaps that become apparent now that we are years removed from it. So I'm afraid that reading it would be a very fragmentary experience -- or, in order words, the experience as I envisioned it cannot be recovered. It's gone, the moment is gone, the context is gone, the dance between writer and participative reader is over and everyone's gone home, and I don't know if something comparable can be reconstructed in a way that I'd consider sufficient.
That said, I'm not really embarrassed of my work there. Of course there are all those issues I listed, some resolvable and some not, and there are other things I could also point as issues, but I still look back fondly to what I wrote then. Some excerpts were fantastic and made it into the game in one shape or another, Oscar's introduction being one of them, and it had a kind of chemistry which I cannot think ill of. In a sense, the core of what I wrote there became the seed for the fantastic things we've worked on for years now, and whatever flaws I can point do not detract from what I accomplished then.
Maybe once I'm done with Minotaur Hotel I could set aside a month or two to go back and thoroughly reedit the whole thing -- keeping the original text more or less as-is, but combing through the archives of threads to at least recall things and connect things better. Adding in comments too. Who knows, we'll see. I don't want to plan that much ahead because lately I've already been looking back to it with a greater fondness for certain aspects I once considered bad, and I've made my peace with them. I'm giving myself the time I need.
Onto your second question, things changed a lot from the original 4chan quest to the current VN format, but the core of the story remained the same. Once we started developing it as a game, however, we pretty much stuck 95% to "the plan".
Yes, the old man at the start was always planned to be Poseidon -- we left in plenty of foreshadowing from the very first builds. Originally the location you were in (either a train or bus station) changed halfway through the scene and that was a clue to the magical things happening. We later edited that out because it confused people too much but we still kept the sudden moments of lucidity, which are when Poseidon is capable of trying to lie to you about his history.
The Olympians' involvement has remained almost the same as we originally planned. They're going to show up later in the story -- what has changed is that they'll now be introduced one by one during Act 3, those elements are reasonably late additions. The visit to Mt. Persephone is "also" a reasonably late addition, dating back "only" to the time when Asterion takes the MC to the underground and they wrestle (which was many years ago by now, you can see that even the things we did change were thought out well in advance).
I suppose one of the biggest changes from quest to VN was the addition of Themba (who fleshes out Asterion's history), Khenbish (the most normal guy in the cast) and Pedro (Pedro) who together made the game much more resonant with myself. They're the Global South crew who pulled Minotaur Hotel away from the geopolitical broadness that was easy for anyone to swallow and into the more magical realist tone that I wanted to impart onto the game. The Hinterlands in particular did not exist in the quest and Storm arrived on his own at the end of the quest, and a different character called "Black" served his role in helping Asterion develop as a character.
You could say that, in making Mino Hotel into a VN, I was able to show more of myself and my own thoughts as a writer. The VN version is more sincere, at times it feels as though I've taken off the training wheels and I'm capable of pulling off all the advanced tricks I know myself to be capable of executing.
And yes, there are cut characters. There was a jackal and a cosmic bird who I did not have much fun writing, and also a slug I did not develop very much, plus a big and very sad lizard. There was a hydra, the "Black" I mentioned, but they're coming in as a recruitable character during Act 3.
The House of Asterion was an inspiration, yes. Check out the other answers in this Q&A, we mentioned it a few times already.