Plunge into Winter

• WOTC Official Reminder Textofficial rules
  Scry — Look at the top N cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.

• WWizards of the Coast2023-09-01
  Official Ruling
  If the target is already tapped at the time Plunge into Winter resolves, you'll still scry 1 and draw a card.
• WWizards of the Coast2023-09-01
  Official Ruling
  You can cast Plunge into Winter without a target just to scry 1 and draw a card. However, if you do choose a target, and that target is illegal at the time Plunge into Winter tries to resolve, the spell won't resolve and none of its effects will happen. You won't scry, and you won't draw a card.

Rulings via Scryfall