when we must replace the regedit /s, do we also need to have setconsole("hide") in our function?
No, you don't need that. I was imagining a simple UDF that runs the .REG files fed to it and returns an error code inducation whether the file was imported correctlt or not (e.g. file not found). Since REGEDIT /S doesn't tell you if some imports haven't been doen because of syntax error, it is not necessary for the UDF to do this either.

Finally, I didn't put all types of registry entries into the test .REG files, just the most important ones. So, a UDF posted into the UDF section might need to contain those cases, too, but for this exercise, it is not necessary.
There are two types of vessels, submarines and targets.