Can you respond to spells on the chain after other spells/abilities have been added on top of them, and does the chain resolve one by one with opportunities to react between resolutions?

Ruling: You can target any spell on the chain at any point, even when other spells/abilities are on top of it. The chain resolves one by one, and between each resolution you have the ability to react again.

Sequence:

• Spells/abilities are added to the chain
• The chain resolves one item at a time (top to bottom)
• Between each resolution, players can react and add new spells/abilities to the chain
• This continues until the chain is empty

Nuances:

• While you can respond to any spell on the chain at any time, it's strategically better to wait as long as possible to avoid giving your opponent unnecessary information
• You can let one spell resolve, then respond to remaining spells on the chain before they resolve