Experimental Frenzy

Official rulings

1. If the top card of your library changes while you’re casting a spell, playing a land, or activating an ability, you can’t look at the new top card until you finish doing so. This means that if you cast the top card of your library, you can’t look at the next one until you’re done paying for that spell. (2018-10-05)
2. You must follow the normal timing permissions and restrictions of the cards you play from your library. (2018-10-05)
3. You can play a land card on top of your library only if you have available land plays remaining. (2018-10-05)
4. Experimental Frenzy lets you look at the top card of your library whenever you want (with one restriction—see below), even if you don’t have priority. This action doesn’t use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand. (2018-10-05)
5. You’ll still pay all costs for a spell you cast from your library, including additional costs. You may also pay alternative costs. (2018-10-05)
6. You can’t cast spells or play lands from your hand, but you may take other actions with those cards (such as discarding them to activate their cycling or bloodrush abilities). (2018-10-05)