Quicken

• WWizards of the Coast2006-02-01
  Official Ruling
  You don't choose a sorcery card when Quicken resolves. Rather, this sets up a rule that is true for you until the turn ends or until you cast a sorcery card, even if you cast that sorcery at a time you normally could.
• WWizards of the Coast2006-02-01
  Official Ruling
  If you cast multiple Quickens on the same turn, they'll all apply to the very next sorcery spell you cast.
• WWizards of the Coast2006-09-25
  Official Ruling
  After Quicken resolves, you can Suspend a sorcery in your hand any time you can cast an instant. As soon as you actually cast a sorcery, you lose this capability.

Rulings via Scryfall