This feature will appear at random. There is no other way to trigger its appearance.
Once clicked, the Gamble Menu will open. In this menu, you have to guess what the colour or suit is of the card in the centre.

If you guess the colour correctly, you will receive 2x your score.
If you guess the suit correctly, you will receive 11x your score.
If you get the answer incorrect, you will lose your score; your score is set to 0.

Yes.

Tip: When Gamble Menu is closed, the timer gets pushed back equivalent to 2x lightning strikes. This will occur after you click on 'Return' without guessing or after a failed attempt.