Twin Bolt

• WWizards of the Coast2015-02-25
  Official Ruling
  You choose whether Twin Bolt has one target that will be dealt 2 damage or two targets that will each be dealt 1 damage as you cast Twin Bolt.
• WWizards of the Coast2015-02-25
  Official Ruling
  If you cast Twin Bolt with two targets and one of those targets becomes illegal before Twin Bolt resolves, the remaining legal target will be dealt 1 damage. You can't change the original division of damage.
• WWizards of the Coast2025-04-04
  Official Ruling
  You choose whether Twin Bolt has one target that will be dealt 2 damage or two targets that will each be dealt 1 damage as you cast Twin Bolt.
• WWizards of the Coast2025-04-04
  Official Ruling
  If you cast Twin Bolt with two targets and one of those targets becomes illegal before Twin Bolt resolves, the remaining legal target will be dealt 1 damage. You can’t change the original division of damage.

Rulings via Scryfall