How many passes to end the game
In theory (explained later) a game should end after 3 passes, but different rule sets have different rules about this point.
But here the discussion is more fundamental.
The main problem is what happens with a ko after a pass.
Suppose Black just played , capturing , White passed and Black passed as well.
If the game ends with 2 passes, the game is over. If, however, White has to make the last pass, may she now retake the ko instead (and continue the game) ?
(If the game ends after 3 passes, Black could do the same if the colors were inverted.)
The easy answer of course is that Black should have captured any of the stones after White's pass (teire), but prescribing moves is a bit against the grain of the game (and teire is only prescribed in Japanese rules).
And why is Black not allowed to makes mistakes?