a few questions :

can the ace be used as a '1' ?
i mean : is A-2-3-4-5 considered to be a straight ? (or nothing)

are there situations where more than 5 cards are used to determine the winner ?
for example :
player A has in his hand 2 and 10
player B has in his hand K and 10
on the table is 6,7,8,9,Q
will the pot be split (both players have a straight) or will player B win with his (6th card) K ?

whats the minimum amount you need to play in a game ? as much as the big blind ? or more ?
(i am not talking about how much you need to join the table, but amout the amount you need to participate in a game when you are already on the table)