The last scenario (with Saboteur and IGG) is a little different, since the Curse gaining is an effect of IGG, not of Saboteur. I asked a similar question some years ago: If you Moat a Cultist, and your opponent uses that Cultist to play another Cultist, do you have to reveal Moat again? The answer is yes: even though the second Cultist was played as an effect of the first, the effects (giving Ruins) of the second is not part of the effects of the first. So the answer in the Saboteur scenario is that C gains a Curse.
As I said, the Bureaucrat question is different. Here the revealing is also part of Bureaucrat's effects, just like the topdecking. The question is if your opponent seeing your revealed cards is considered to be part of the effect of revealing those cards and that this affects your opponent. Obviously the intention is that you get to see them, however we would formalize the rule.