Every puzzle
Fifteen puzzles in all. Three of them appear every single day, and the fourth slot is a Wildcard that rotates weekly through the other twelve.
Every day
The same three, in the same order, for everyone. They are the ones worth getting good at, and the ones the day board scores.
The Wildcard
One of these takes the fourth slot for a week at a time. Which one is announced by the app rather than guessed, and the rotation is published ahead of the week it applies to.