Like the title suggests i was wondering if it is possible to warp to the singleplayer levels in the 2 Player Versus Mode. I know about the area overflow bug and the one where you can go to previous areas. But is it possible to go to all or at least some of the singleplayer levels?
Because if so i'd make a Hub World in my versus hack with warp pipes that leads to all kinds of levels where you can fight against your friend instead of just the normal amount of 5 (or 10 like in the rom hack newdevluigi made (https://nsmbhd.net/profile/1650-newluigidev/))

I've experimented with this idea but unfortunately no.
The hack you linked is the closest we have to having more levels in MvsL.
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Ok, i experimented with this idea and found out that you can using this method:
https://nsmbhd.net/thread/1823-area-overflow-bug-going-to-any-level-of-current-world-area-overflow/
In summary:
you need to go to Block 6 of your levels hex editor, resize the window so there are 20 bytes in each window. The 20th byte of each Row in now the world the entrance leads to like shown in the image below.

I now made the standard 5 versus levels into the same hub world that contain pictures of the levels that you can go into (like in sm64). By putting the course select to "Random" in the ingame settings you now get always get warped back to my hub world after Mario or Lugi wins. The Castle and Tower Levels crash for some reason so you cant replace them with your versus levels.
This is the hub world with pics you can jump into:
(the top levels are duplicates with the difference that the only item you can get is the blue shell)


However i can not really share it by now since it also uses levels and tilessets from other creators here that have been used to play private. But sooner or later i will contribute my part to this community and share stuff i made.