Just checked mine, from the main screen there is the pull down menu, at the bottom of the pull down menu is a button for photo frame. Once in that menu hit setting, then scroll down and there is a night mode start time and night mode end time.
Not sure about his but mine does the same. Screensaver of rotating pic until around 11pm then the screen goes black until morning, then the screensaver comes back on.
Just got installed this past spring, looks like it is the same system you have. As for the siren, I haven't tested that yet and wont have the opportunity for a while. But will when I can.