Molten Disaster

• WOTC Official Reminder Textofficial rules
  Kicker — Kicker [cost] (You may pay an additional [cost] as you cast this spell.)

• WWizards of the Coast2007-05-01
  Official Ruling
  If Molten Disaster was kicked, Molten Disaster has split second as long as it's on the stack.
• WWizards of the Coast2021-03-19
  Official Ruling
  After a spell with split second resolves (or otherwise leaves the stack), players may again cast spells and activate abilities before the next object on the stack resolves.
• WWizards of the Coast2021-03-19
  Official Ruling
  Split second doesn't stop triggered abilities from triggering, such as that of Chalice of the Void. If one does, its controller puts it on the stack and chooses targets for it, if any. Those abilities will resolve as normal.
• WWizards of the Coast2021-03-19
  Official Ruling
  If the resolution of a triggered ability involves casting a spell, that spell can't be cast if a spell with split second is on the stack.
• WWizards of the Coast2021-03-19
  Official Ruling
  Casting a spell with split second won't affect spells and abilities that are already on the stack.
• WWizards of the Coast2021-03-19
  Official Ruling
  Players still get priority while a card with split second is on the stack; their options are just limited to mana abilities and certain special actions.
• WWizards of the Coast2021-03-19
  Official Ruling
  Players may turn face-down creatures face up while a spell with split second is on the stack.
• WWizards of the Coast2024-11-08
  Official Ruling
  To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.
• WWizards of the Coast2024-11-08
  Official Ruling
  If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.
• WWizards of the Coast2024-11-08
  Official Ruling
  The kicker ability doesn't let you pay a kicker cost more than once.
• WWizards of the Coast2024-11-08
  Official Ruling
  If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.
• WWizards of the Coast2024-11-08
  Official Ruling
  If a spell's kicker cost was paid, the spell is "kicked."
• WWizards of the Coast2024-11-08
  Official Ruling
  If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.

Rulings via Scryfall