How does Promising Future resolve when both players choose cards to play, particularly regarding timing, the chain, and whether cards can be reacted to?

Ruling: When Promising Future resolves, both players choose cards face-down, then play them in turn order (starting with the next player, so the opponent plays first in 1v1). All cards played by Promising Future resolve as part of that spell's resolution and cannot be interrupted or reacted to by other cards.

Sequence:

• Promising Future begins resolving
• Both players choose cards face-down from the top 5 of their deck
• Starting with the next player (opponent in 1v1), each player plays their chosen card in turn order
• Each card resolves completely before the next card is played
• All of this happens during Promising Future's resolution
• Promising Future goes to trash
• Any triggered abilities from units played this way go on a new chain after Promising Future finishes resolving

Nuances:

• If you cannot pay the power cost of your chosen card, you recycle all 5 cards and cast nothing (if you can't perform an instruction, you ignore it)
• Spells played via Promising Future cannot be countered by cards like Windwall or Defy because nothing can be added to the chain during another spell's resolution
• Windwall chosen from Promising Future itself would have no effect because there would be nothing on the chain when it's played
• You cannot flip hidden cards or take other actions during Promising Future's resolution
• This same principle applies to other effects that "play" cards, like Kai'Sa Evolutionary