How the app updates itself
The app has two parts that update in different ways.
The screens
Each time it starts, the app checks with LutraCAD whether there is a newer version of its screens and downloads it if so. You see checking version and then a percentage while it does. This is why a screen can change without an App Store update.
The app itself
The scanner and the camera come from the App Store, so those follow a normal App Store update.
Without internet
The app starts with the screens it downloaded last, and everything except logging in, the form and uploading works as usual. Only on a first install is a connection required: without one the app cannot download its screens yet and reports First boot requires a internet connection.
Update required
If the installed version is ever too old to keep working safely, a full Update required screen blocks the app, and Update now opens the App Store page so you can install the new version.