Do you think it is possible to hack or glitch to the other side of those blocks? Probably- no, definitely won't do anything, but I'm curious.
Viewing post in you can open the white blank door in world 12!
yes, it is, with undertalemodtool. theres an entire hub in there, although unfinished. its called autumn woods, and the levels in it are called pages. all the levels are empty. (see https://iwannalockpick.fandom.com/wiki/Unused_Content#Autumn_Woods_Hub)