No, you cannot put a black card on top of another black card in Uno.
No, in Uno, you can only put down one card at a time.
Yes, in the game of Uno, you can say "Uno" before you put down your second-to-last card.
During your turn in Uno, you can put down one card.
No, you cannot put a reverse on a Draw 2 card in Uno.
No, in Uno, you cannot put a 4 card on top of a 2 card.
No, you cannot put a wild card on a Draw 2 in the game of Uno.
No, you cannot put a wild card on a Draw 4 card in Uno.
No, you cannot put a Skip card on top of a Draw 2 card in Uno.
No, you cannot put a Skip card on top of a Draw 4 card in Uno.
No, you cannot put a skip card on top of another skip card in Uno.
In Uno, you cannot put a Wild Card on top of another Wild Card.
No, in traditional Uno rules, you cannot put down two wild cards at the same time.