Complete Exploration of World 256: World 0

Current Information about World 0
As of right now, a lot of people are already familiar with World 0. It's number '0' is a placeholder spot for 256, and many people agree there's only one level, and it's the true final level. World 0-1 is an underwater clone of World 4-4, and when you complete it, the level softlocks. That being the 'ending' of the game.

That's more of World 0
I wasn't satisfied with that ending. My definition of an ending is: So I looked through the internet for DAYS to find codes that could potentially help me bypass World 0-1. I eventually found these codes. This is the list of codes I used and what purpose they each served.
 * 1) The fourth level is a castle level, which takes you to the next level (traditional ending)
 * 2) You get to a level that starts off with a softlock (glitched spawnpoint)
 * 3) You get to a level that crashes (nowhere left to go)

NNXAZZYE + AANAAXZG: This code lets me select any of the 256 Worlds.

SUEISA: This code turns enemies into Powerups. This gets useful when you can't hit '?' blocks.

KILLLU: Jumping or falling as big Mario skips a level. This works well with the code 'SUEISA' and lets players skip levels that loops or softlocks at the end.

Doing this combo, I touched a piranha plant on 0-1 to turn to big Mario, and I went to 0-2. I was able to continue warping just by pressing 'A'. Some levels I wouldn't need to if I spawned falling. After a couple of minutes of skipping levels, I was able to continue this progress until I got to a level that crashed. That level was 0-- (or 256-40) the fortieth level on World 0.

Each level in World 0
I eventually went back to see what each level was a duplicate of. I wasn't able to identify all of the levels, but this was what I have concluded as the OFFICIAL range of levels in World 0.

List of World 0 Info:
256-1 to 256-2: Underwater 4-4

256-3 to 256-21: Underwater 2-4

256-22 to 256-27: Normal 4-3

256-28 to 256-32: Normal 8-3

256-33: Normal Underwater Level (Unidentified)

256-34: Underwater 4-3

256-35: Underwater 1-2

256-36: Underwater 4-4

256-37: Underwater 6-2

256-38: Underground 2-4

256-39: Normal 1-2

256-40: (Crashes)

Level Types Info:
Underwater: 27

Ground: 9

Underground: 1

Normal: 10

Castles: 22

Level Appearances: 7 (1-2, 2-4, 4-3, 4-4, 6-2, 8-3, and 256-33)

Conclusion
With that being said, that's the true ending to Super Mario Bros. The final level nobody was able to discover. I hope that this page helped expand your imagination and wonder about codes and gaming. I hope people publish their own content exploring 256-40 and maybe even try doing this technique on other levels.