2) The action is not discarded, it just no longer affects your minions.
So if a minion of mine had Poison on it which has
Ongoing: This minion has -4 power (Minions have a minimum power of 0)
and I play Wildlife Preserve
Play on a base. Ongoing: Your Minions here are not affected by other player's actions.
Does this negate the Poison? or is it only new Actions played afterwards that do not affect my minion? Also if it is the former I take it that the Poison card stays on the minion and is not discarded then.