"R" initialises the display to the download position.
Each button (1-12) will activate at least one light cell but it may illuminate more. Note also that, while two switches may engage an individual bulb and so light it, any more will extinguish it.
A switch is 'ON' when its indicator changes from [O] to [ I ].
Determine the number of levels of security, the button combinations and provide a rationale for all solutions when the display is fully lit with no bulb activated by multiple buttons, otherwise a combination is void.
[Consider each button and its light(s) as a unique event which are not shared by another event in the solutions].
Incidentally, every button will feature at least once in the solutions, and if all buttons are on then no bulbs are lit!