Shroudmon

Q:If I have exactly 3 cards in my security stack, do I activate both the "1 of your opponent's Digimon gets -7000 DP for the turn" effect and the "delete 1 of their unsuspended Digimon" effect when activating this card's [When Digivolving] [End of Attack] effect?

A:Yes, that's correct.

Q:How exactly do I perform " until there are 3 cards in your security stack" in this card’s [On Deletion] effect?

A:If you have 2 or fewer cards in your security stack when the effect activates, repeat until there are 3 cards in your security stack. You don't have to do anything when the effect activates if you have 3 or more cards in your security stack.