Calcite Snapper

• WOTC Official Reminder Textofficial rules
  Shroud — This permanent can't be the target of spells or abilities.

• WWizards of the Coast2021-03-19
  Official Ruling
  Effects that switch a creature's power and toughness apply after all other effects, regardless of when those effects began to apply. For instance, if you target a 1/2 creature then give it +2/+0 later in the turn, it's a 2/3 creature, not a 4/1 creature.
• WWizards of the Coast2021-03-19
  Official Ruling
  Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to a creature may become lethal if you switch its power and toughness during that turn.
• WWizards of the Coast2021-03-19
  Official Ruling
  Switching a creature's power and toughness twice (or any even number of times) effectively returns the creature to the power and toughness it had before any switches.
• WWizards of the Coast2024-11-08
  Official Ruling
  A landfall ability triggers whenever a land you control enters for any reason. It triggers whenever you play a land, as well as whenever a spell or ability puts a land onto the battlefield under your control.
• WWizards of the Coast2024-11-08
  Official Ruling
  A landfall ability doesn't trigger if a permanent already on the battlefield becomes a land.
• WWizards of the Coast2024-11-08
  Official Ruling
  Whenever a land you control enters, each landfall ability of the permanents you control will trigger. You can put them   on the stack in any order. The last ability you put on the stack will be the first one to resolve (As a result, you can have those abilities resolve in the order of your choosing.).

Rulings via Scryfall