I was wanting to clear terrain using a script because I had a map and no use for the terrain (Terrain is unable to be unlocked). Now I am wanting to see if there is a script to fix this (In command box) Script used to clear it:
game.Workspace.Terrain:Clear()
CTRL+Z (the undo button) is your best friend. If you already saved over, you can go to your place configuration and revert the place back to an older version.
If you really have to, you could CTRL+A your Workspace in the newest version of your game (which doesn't have the Terrain feature) and paste it over to your older version.
Uhh, if your gonna remove anything again then remember to clone it before removing the original one.
As the person above said, use CTRL + Z or go to your place configuration and revert the place back to an older version.