The 2nd one.
The double switch is generally made to change the batting order. If the pitchers spot is due up the next inning switching two players allows the manager to decide which of the two will bat in the pitchers spot.
In the minor leagues pitchers do not come to bat. They all use the designated hitter rules. In Major League Baseball pitchers come to bat in the National League, they do not bat in the American League where the designated hitter rule is employed. During inter-league play, the All-Star Game and the World Series, pitchers from both leagues come to bat if the game is being played in a National League park.
yes you can change pitchers anytime you want
Yes you can change sides at any time during your at bat.
Inning---but not during an at bat. Although ambidextrous pitchers are extremely rare.
Yes. A switch-pitcher is allowed to change hands during an at-bat. At the start of the at-bat, the pitcher must declare which arm he will throw with so the batter can determine which side of the plate he will bat at. Each player may switch sides one time during the at-bat and must make this known to the umpire-in-chief before-hand.
Yes. If the opposing manager changes pitchers in the middle of an at-bat, the batter is allowed to switch sides if necessary. Otherwise, the batter must remain on the same side he started on for that at-bat.