The top card of your library isn’t in your hand, so you can’t suspend it, cycle it, discard it, or activate any of its activated abilities.

You must follow the normal timing permissions and restrictions for the top card of your library and pay its costs. If it has alternative or additional costs, you may pay those. If the card has any mandatory additional costs, you must pay those.

If the top card of your library is a land, you may play that land only if you have any available land plays.

If the top card of your library changes while you’re casting a spell or activating an ability (perhaps because that top card is the card you’re casting) the new top card won’t be revealed until you finish casting that spell or activating that ability.

As soon as you finish playing the card on top of your library, reveal the next card in your library.