Hi there, good question, you probably need to download the latest zip and play with that (it will keep your settings and save files, though save files tend to become invalid between major updates). You can use the itch.io client to keep it up to date automatically.
Are you sure that's the version you're running? If you go to wherever you unzipped the game to and open the changelog.txt file, what is at the top? It should read
Alpha 4.2.3 - 24th November 2020 - Fixed a crash when deconstructing a wall that was not constructed - Fixed an issue with map generation for very small maps
If it's the latest version. In fact the text in the bottom left of the main menu tells you which version it is. I've just downloaded and run the game through Itch.io myself to check and it is Alpha 4.2.3 for me as expected. Perhaps you've a shortcut or something pointing at an old version?
Saved game management is the feature I'm working on right this minute, so while it's painful to do in the current version (you can do it by taking a copy of the quicksave.save file in the King under the Mountain/saves directory, most likely in your documents.
The river being stone is an extremely rare bug that I need to capture a map seed for to recreate so I can investigate and fix it.