In most games, yes. Many also allow it to be either above or below (e.g. in blackjack it can be worth 1 or 11, king is worth 10; in Poker it can be used above the king or below the 2).
However, some games fix the value of the ace as below the king. This is the same as seeing it as a 'one' card for those games.
A poker hand with an ace high or an ace kicker (tiebreaker) will win over a poker hand with a king high or a king kicker.So yes: in games such as Texas Hold'em or seven-card stud, having A-3 as your hole cards is marginally better than holding a K-9.
In poker, a straight is not always the best hand. A king, ace, 2, 3, 4 sequence, known as a wheel or a bicycle, can beat a straight.
6/139,7
Yeah
ace wins
yes. it also beats any "3 of a kind"
yes
Yes, in some variations of poker, such as in games like Omaha and Stud, the ace can be both high and low.
No.
yes
No, Ace is the highest card in the deck and a two is the lowest.
No. The ace of spades is the highest ranked card in Texas hold 'em.