You can get to the menu 2 ways. Car in "Ready to Drive" mode, hold BC button on stalk in for 20-25 seconds to bring up the menu. Quick press BC button to scroll through options, long press (5-10 seconds) to select item. Nothing that interesting. To enable the "disabled" items, put car into diagnostics mode then hold BC button for 20-25 seconds. Showroom mode just has various videos playing in random order showing the concept car and a some features (like gesture control which i4's don't come with). Tap the screen if you want to jump to the end of the current video. Chassis Dyno mode use at your own risk. Brake service mode useful for those who like to service their own car.
There is no "Unlock" menu item... maybe requires a different sequence?
JC