Forum:Drastic Drop Off Explanation

I recently discovered the card "Drastic Drop Off", and now I have some problems understanding its effect, so I want to be sure I get it right. So, everytime my opponent adds a card(s) from his deck to hand, including drawing for his Draw Phase, I can activate and make him discard the added card or 1 of them if more than one. But this are the rulings I want to confirm: Thanks a lot for helping me understanding this card, if you think of other situations worth mentioning, please do so! Thanks in advance, again. Kentaru Z (talk • contribs) 14:20, March 19, 2015 (UTC)
 * If added 2 or more cards, my opponent chooses the card to be discarded, right? It is not random.
 * I can only activate this card if the effect that adds the cards happens at resolution, not the moment of activation, correct?
 * On the same not, against cards like "Allure of Darkness" or in case the second effect of "Preparation of Rites" is activated, I can't response because I will miss the timing.
 * Can I activate against "Pot of Duality" or similar cards?
 * I believe I can, but in a long chain, that includes a "Dark Bribe" of mine, can I activate this card?