Space Alert

Yes — you may change the cards you played any time before you end that phase; once you pick up the next phase's cards you can no longer change the previous phase's planned actions (page 2).

You may announce “Oops, I tripped.” and perform the action you intended instead of the mis-played one, but your next turn's action is delayed (page 4).

A delayed action is moved one turn later, pushing any card already in that spot forward as well; this cascades until an empty space or until a card is pushed off your last turn, in which case that action is lost (page 4).

No — while in space you are not in any station or zone, so threat effects that knock out, delay, or otherwise affect players on the ship (including computer-maintenance delays) do not apply to you; interceptors attack on the turn you take off and you may take interceptor actions while in space (page 4).

Each zone has six damage tokens; if you must draw a seventh the zone is destroyed and the crew immediately loses the game; damage also reduces system effectiveness as described (page 6).