Mirror of Fate

• WWizards of the Coast2009-10-01
  Official Ruling
  You don’t choose the exiled cards until Mirror of Fate’s ability resolves. It doesn’t matter how they wound up in the exile zone.
• WWizards of the Coast2009-10-01
  Official Ruling
  Exiled cards are face up by default; they’re face down only if the effect that exiled them said so. For example, the cards from your library that Mirror of Fate exiles are exiled face up.
• WWizards of the Coast2009-10-01
  Official Ruling
  You choose the order that the chosen cards are put on top of your library. You don’t have to show anyone else that order.

Rulings via Scryfall