As a standard policy here, anything game specific doesn't belong in Tool-assisted laboratory. It belongs in the appropriate game thread.
Second,
this is how we currently handle the 1st key. Review the method if you haven't already.
Finally, an explanation on loading zones. (
We might need to link explanations everywhere the TAS goes)
The castle area is broken into several areas:
* Outside castle front
* Main lobby area
* Boo's garden
* Underground area
* Upper areas
The only way to transition from one of these areas to another is through some sort of loading trigger. All such triggers in the castle are by opening doors.
The reason the Backward Long Jump (BLJ) works from entering lobby to Bowser in the Dark World is because that hallway is loaded along with the lobby. That type of door is merely a transition of position, not areas. We can already change position with the BLJ, so we skip the door object in our way. Same for Bowser on the Fire Sea, and on the way up after getting through the key door on the way to Bowser in the Sky. Or any of the star doors between us and any of the worlds.
Both key doors are triggers for area transitions, an entirely different type of door. If we glitch through them, we do not trigger the proper opening animation. Without this opening animation, we don't trip a loading trigger. As a result, the next area remains unloaded, and all we achieved was trapping ourselves in a tiny chamber behind the door. There's no trigger for Mario to walk into, he has to physically open the door, and only a key can do that.
The ground floor of the castle is trivial to enter, I don't feel the need to list them.
Basement has two known access points:
* Key door
* Moat door
Technically, it has more access points, in the form of dying or collecting a star in each of the courses it contains, but there hasn't been any known way of reaching those without first reaching the basement.
The moat door has the advantage of not needing the key, so Mario can open it without first needing to beat a Bowser. The key door is the only other access point, and there is no way to get through that door without the key, as explained above, it's opening the door itself that gets our transition, not glitching past it.
To reach the upper floors:
* Key door
Other than the courses contained up there, we have no other way of getting a transition there. The BLJ is decidedly obvious with the nearby terrain, but thanks to the fact opening the door is itself a trigger, we would only throw ourselves into a small chamber and can't advance any further. You apparently intuited this, or perhaps had another reason, or else this suggestion might have come up instead. The same reason applies to the basement key door.
I hope this detailed explanation helps you understand why your suggestion fails.
