The apps are repackaged as single executables that run without any prompts. They just pop up, and display a progress bar as they install. These application packages include the registry key for checking

su is used to install the packages with admin rights as bleonard said.

the only place i could see where y: is used rather than the variable is at the start of login.kix where all the variables are defined

the reason why the smaller script files such as complete.kix exist, is that we setup sites for a number of different clients, and this way makes it cleaner if we have to add customisations to those parts of the login script. it seems a bit off in the base configuration, but where these customisations are used, its much nicer.