Is the card I reveal the card (or the first card) I draw?
[Source: WotC]
Yes. Whether it has a blue battle icon or not, it will the card you next draw.
Several cards in this set put battle cards under characters on the battlefield. If my opponent does this, and one of those cards is a Secret Action, will Sergeant Mirage’s ability see it and give him Tough 2?
[Source: WotC]
No. Sergeant Mirage’s ability looks only in the played area. Secret Actions that somehow end up in your opponent’s KO area, scrap pile, or under a character on the battlefield don’t count.