>Will the scheduler start the application also when the server is being restarted due to a Windows upgrade, and nobody logs in?

IIRC, there's an option to run the app again after a set time if the first run fails or is skipped. Another option (which I always used for unattended operation) is to run regardless of whether the user is logged in or not. So it should run when nobody's logged in. Just like many system level scheduled tasks (in some distributions) run under accounts which are actually never logged into - various system accounts, often with $ or SYS in their names.