21) Reverse works like a Skip, and when you use a Skip, you can play another card immediately
22) When the first card to be placed face up is the Reverse card
23) Yes, when you suspect a Wild Draw 4 Four card was used incorrectly
24) Draw two cards
25) Higher
26) Lower
27) Wild Draw Four
28) A Wild Draw Four card cannot end a game
29) All are official UNO rules
30) All of the statements are false
31) Cat UNO