how does diana lunari work? do you check and recycle optionally before reveal?

Payment is on finalization and not on resolution.

Yes — you Predict first (look at the top card and optionally Recycle it), and only then does the reveal happen. Full sequence: when a showdown begins at Diana's battlefield, her triggered ability goes on the chain. On finalization you may pay [1]; the payment is optional, and per the Vendetta rules update you can decline even if you have Energy floating (Rule 444.2). If you pay, you [Predict] — look at the top card of your Main Deck and choose whether or not to Recycle it (Rule 436.1). If you Recycle it, it goes to the bottom and the "reveal the top card" then shows the new top card; if you don't Recycle, you reveal the card you just looked at. If the revealed card is a spell, you draw it. It's a single dig — no repeated Predict. Two things people get wrong: the Predict look is private while the reveal is public (opponent sees that card), and declining the [1] means the whole thing is skipped, including the reveal — the reveal is part of the paid effect. Note the trigger fires off any showdown at that battlefield, including a non-combat showdown from moving onto an empty battlefield (FAQ #9373), and it still resolves even if Diana is removed after the trigger is on the chain (FAQ #10222).