Ok some more theories:
is the blacksmith house in lorule right before the hilda text a cutscene room, cause if it is, then I don't think we can get access to the hilda text
If you all could convince loopy to sell me a 3DS XL capture card, I could record things for you guys to see =^_^=
You are exactly right, Ahamplan. I just confirmed earlier this morning that the Lorule availability flag is set by the mini-cutscene in the blacksmith's house. This cutscene does not happen unless the major cutscene where Yuga becomes Yuganon has already played. However, we were wrong about one thing: doing the Yuga to Yuganon cutscene with zero health *does* have an effect!
This sequence of steps leads to interesting, but ultimately useless, behavior:
1. Beat Yuga 2 in Hyrule Castle.
2. Go to Lorule the usual way via Zelda's office.
3. Drop to 1/2 heart (or 1/4 if you have the Blue Mail).
4. Stand in the Lorule Castle tower's entrance very close to where it will take you in.
5. Set a bomb while facing south, so that it takes the last of your life as it knocks you into the room.
6. Either let the Yuganon transformation plus Hilda introduction play through, or skip it.
7. You will die once the cutscene finishes.
8. Continue, which'll take you to your house.
This glitch has been known for a while. (Was it you who found it, Ahamplan?) It's known that Lorule has not activated doing this, and you can repeat the Yuganon cutscene to continue normally. But it is not the case that this did nothing!
If at this point you go to Lorule by means other than Hyrule Castle again (I went through the Stylish Girl's house), the music is still playing the longer intro. If you then go into the Lorule blacksmith's house, it triggers the cutscene! The Yuganon transformation cutscene appears to set a flag that causes the blacksmith house cutscene to play if you go in there.
There is secondary evidence I've found that shows that the blacksmith cutscene is the master key. This evidence can easily be tested without a hack, too. Beat Yuga 2, play/skip the Yuganon transformation scene, then kill yourself using bombs within the blacksmith's house. When you wake up at your house with Ravio and go outside, Sahasrahla will be there and the portal will be active.
From this point, just take the portal, then head for the Lorule blacksmith's house. You'll notice that despite Lorule being active, the Dark World music is still playing its extended intro. When you get right in front of the blacksmith, Hilda's message appears. This fixes the music to skip the intro after that first time. Here's a screenshot of me getting Hilda's message from the south rather than by exiting the blacksmith's house. Despite this obviously coming from a hack (I'm wearing the Blue Mail I got by going to Swamp Palace early), I again believe that this is possible to do without a hack. I haven't tested it, though.
https://miiverse.nintendo.net/posts/AYMHAAACAAAYUKltKvEcNQSadly, it appears that the Lorule active flag that is set by the blacksmith's wife cutscene controls both the portals and the back wall in Yuga 2's room. Therefore, I conclude these things:
1. The cutscene with Link waking up to the Lorule blacksmith's wife is the master Lorule trigger.
2. Yuga 2's back wall closure is the same flag or at least set simultaneously with the Lorule master flag.
3. Hilda's speech does nothing except apparently set a flag causing the Dark World music to not play the intro the next time that area loads.
4. We didn't notice #3 because the only place in which a Hilda message skip is currently possible is on Death Mountain, where the music has nothing special the first time it's played. If I'm wrong about this being the only place, then this theory can be tested without hacks.
5. It does not appear that anything useful is gained so far by going through the Stylish Lady's house...unless for some reason you want the Blue Mail during the Hyrule part of the game.
I still need to somehow delete the north wall of Yuga 2 to see whether an early Yuganon is possible if we can clip through the wall or go out-of-bounds. Deleting the wall is one way to test it; another is to reprogram Yuga 2 to spawn Armoses instead of soldiers.
I have no insight into the contents of data files in terms of models and loading areas. Sure, I have access to the raw files, but they're in a format I don't know.
If there's anyone with a Gateway card and <= 4.5 3DS firmware on one of their 3DS's, I could set them up with tools to mess around with this themselves.
Melissa