First of all, the level skip cheat is "theresnoplacelikeoz". If anyone lists cheats that are only for the demo, they're mistaken, as I don't believe there were ever any demo-exclusive cheats.

But second, it's not necessary to use that code to determine whether the new maps are still present. You can confirm Toploader's correct assertion without even entering the game, simply by going to your installed game folder and navigating to "res\levels\single" and checking that there are at least 40 items in each of the 3 folders there (easy, medium, hard). This is because each map requires 2 files in each of the 3 difficulty folders - excluding the final map's files, which are contained in the "hard" folder - and the original game had 16 maps (32 files). Adding the 4 new maps (8 files) equals 40 total files.

Yes, I checked, and yes, they're all there. And thus I find it highly annoying that Cheater87 ever suggested otherwise without even bothering to check, but also highly understandable given the fact that the option to load maps directly from the game seems to have been removed entirely - which is a whole lot more annoying. Also annoying: the new behavior of the game when reaching the conclusion of gauntlet maps (What the hell...) and the inablity to avoid the delay of the opening screens.

But the reason the "Special Delivery" maps directly succeed the original maps is actually because this new version is just Postal Plus with the option to play the un-expanded original game removed, and with the game's map-loading capability utterly broken. In Postal Plus, the player always had the option to play through the game with the "Special Delivery" levels tacked on to the end, and so regarding the order of the maps themselves, absolutely nothing has been changed in this new version.

For the record, the 4 "Special Delivery" maps are:
EZ Mart
Shanty Town
Earthquake
La Palamino Resort

Not that you can load any of them individually.

And where did the editor go? At the very least, its executable is now missing entirely, though its documentation and resources seem to remain.

I was excited to see this update and be able to return to using keyboard controls on my newer systems, and I genuinely appreciate the mostly excellent work that the Running with Scissors team has done to update this classic for modern systems, but I'm quite relieved that I never got rid of my older, differently-buggy but vastly superior GOG installer. I was rooting for this update to be perfect and to resolve every issue experienced when trying to play the game on newer systems, but I'm sorry to have to say that this new GOG version still has a plethora of issues and still needs a lot of work. And with all of its major problems, I find it hard to believe that it was ever actually tested by anyone who had memory of how much better the previous version worked.