Counterlash

• WWizards of the Coast2011-01-22
  Official Ruling
  If the card has in its mana cost, you must choose 0 as its value.
• WWizards of the Coast2011-01-22
  Official Ruling
  If you cast a card “without paying its mana cost,” you can’t pay any alternative costs. You can pay additional costs, such as kicker costs. If the card has mandatory additional costs, you must pay those.
• WWizards of the Coast2011-01-22
  Official Ruling
  You cast the card in your hand as part of the resolution of Counterlash. Timing restrictions based on the card’s type (such as creature or sorcery) are ignored. Other restrictions are not (such as “Cast [this card] only during combat”).

Rulings via Scryfall