Is my opponents card order the same for me as for him?
Solution 1:
Yes, the cards in your opponents hand are in a fixed order. They are sorted by the time he/she drew them, with the leftmost card being the oldest. If you pay attention you can determine which turn the played card was drawn. There are a couple of tools that can help you with this such as Decktracker, which shows you which turn each card in your opponents hand was drawn.