Is the game always finished when a +2 card is placed as the last card?
If a player places a +2 card as the last card, he has won the game. Even if the next player could also place a +2 or +4 colour card. The game ends when the last card is placed. The next player should not answer a +2 card with another +2 card during the game, because there is always the obligation to draw cards.
The exception is the UNO variant „Cumulate“. If this is used, +2 and +4 cards can be extended. Here the following applies: +2 cards can only be extended with +2 cards and the same applies to +4 colour cards. These may not be combined. The extension of a +2 card with a +4 colour choice card is not allowed when „Cumulate“ is used.