Hi Drake-r8, welcome to the forum!
In the older version I have it was only possible to edit games AFTER the level was completed
Oops?! That's strange, there should be no such limitation in any version of the game. However, there is a limitation that prevents editing those levels that come with the game package (which are then reported as being read-only when attempting to edit them), to prevent accidentally overwriting custom changes when updating the game.
but this could be changed by manually editing the level sets
Yes, if you explicitly disable the "read-only" state, you can edit them. Another way to edit them is to simply move the level set folder to your personal R'n'D data directory (and probably also renaming it, to prevent potential naming conflicts with the original level set from the game package).
I want to download the new version but only if levels can be freely edited
The latest version is unchanged in that regard -- just do the same steps as before to edit levels that are reported as being "read only" when trying to edit them. (If you have already edited non-personal level sets in your current game installation at their original location, make sure to not overwrite them when updating the game. When in doubt, just use the "zip" version of the game and play from the extracted folder, which does not overwrite anything (in comparison to the "setup.exe" style version of the game package).)
Hope that helps! If you need any further help, just let me know!