In Uno, you cannot stack a "Miss a Turn" card on top of another "Miss a Turn" card. When a "Miss a Turn" card is played, the next player simply loses their turn, and the game continues with the following player. Each "Miss a Turn" card is treated as a separate action, so stacking them is not allowed.
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, you cannot put a Draw 4 card on top of a Draw 2 card in Uno.
No, you cannot put a Draw 2 card on top of a Draw 4 card in Uno.
No, you cannot put a Draw 4 card on top of a Draw 2 card in Uno.
No, you cannot put a black card on top of another black 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 4 card in Uno.
No, you cannot place a Wild card on top of another Wild card in Uno.
No, in Uno, you cannot play a Wild card on top of another Wild card.