I've tried this step for step and it still didn't reset my world.. Any idea why? Or any other ideas how to reset?
If you're still stumped on this one, that's because your world is NOT in GOG's folder by default, but in the DOCUMENTS folder.
The World.sfc in your default install location will be the exact same size as Eden.sfc. You can copy that one to the Documents folder containing a bigger World.sfc file and overwrite it, and it'll have the same effect as copying and renaming Eden.sfc.
(To know you're in the right folder, look on the Genetics sub folder. If it only has the mum and dad .gen files, it's the default install. If it has moniker (four-character files unique to each norn) .gen files, that's the folder the game stores its changes to the base game in.)
As for using Backup.exe (the Emergency Kit), it DOES try to reset the world... by generating World.sfc in the folder it's in rather than the one the game saves to on a split install, oops. The Hatchery could only be restocked when empty, but GOG's version automatically replenishes it once there's no eggs left. It DOES restock the Health and Science Kits, though.