Skyclave Pick-Axe

• WOTC Official Reminder Textofficial rules
  Equip — Equip [cost] ([cost]: Attach to target creature you control. Equip only as a sorcery.)

• WWizards of the Coast2020-09-25
  Official Ruling
  If there's no equipped creature as Skyclave Pick-Axe's landfall ability resolves, no creature gets +2/+2.
• WWizards of the Coast2020-09-25
  Official Ruling
  Attaching an Equipment with its enters-the-battlefield triggered ability isn't the same as using its equip ability. You don't pay mana for the attachment, and if the Equipment enters at a time you couldn't cast a sorcery, you can still attach it to a creature you control.
• WWizards of the Coast2020-09-25
  Official Ruling
  The bonus from Skyclave Pick-Axe's landfall ability applies to the creature it's attached to at the time the ability resolves. That bonus doesn't apply to a new creature if Skyclave Pick-Axe becomes attached to a new creature.
• WWizards of the Coast2020-09-25
  Official Ruling
  If the target creature becomes an illegal target, the Equipment remains on the battlefield unattached.
• 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.).
• 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
  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.

Rulings via Scryfall