Can you use Windwall to counter an opponent's spell that was played via Promising Future?

Ruling: Yes, you can use Windwall to counter an opponent's spell played via Promising Future when you control the Promising Future.

Sequence:

• When you play Promising Future, both players put their chosen spells on the chain as pending items (opponent's spell first, then your Windwall)
• When Promising Future resolves, the spells finalize in the order they were put on the chain
• The opponent's spell finalizes first, becoming a finalized chain item
• Your Windwall finalizes second and can target the opponent's now-finalized spell
• Windwall resolves first (being higher on the chain) and counters the opponent's spell

Nuances:

• If the opponent controls Promising Future and you choose Windwall, the interaction becomes very complicated due to reverse ordering
• Targeting pending chain items is not explicitly covered in the rules, but would generally be ineffective since items resolve from top to bottom of the chain