Reinforced Shields

[scottaltman9998]

Reinforced Shields says: when this ship suffers 3 or more damage from single attack, repair 1 shield.
I have a few questions:

1) Is this once a round (does when = whenever)
2) Is the trigger optional (if it is once a round must it be used the first time it could trigger)
3) Do repaired shields start disabled if you are cloaked or under the effect of another lower shields effect, like projected stasis field.
4) When is the shield repaired. Before or after the damage is done.