When multiple copies of this card are trashed from the security stack at the same time, does the "when this card is trashed from the security stack" effect on each of those cards trigger simultaneously?
Yes, they trigger simultaneously.
Nov. 1, 2024
Can I process "then, if you have 2 or fewer security cards, place this card as your bottom security card" in this card's [Main] effect even I don't perform "by trashing your top security card"?
No, you can't. If the "by trashing your top security card" condition isn't performed, the rest of the effect isn't processed. In this case, you can't process this effect unless you trash your top security card.
Nov. 1, 2024
