Heroes of Tenefyr

You do not automatically reshuffle during a combat; if you run out of cards you become exhausted and can no longer contribute that combat. All players shuffle their discard piles back into their decks when you leave the Dungeon (whether voluntarily or forced). (Rulebook pp.6, 8)

You may discard your hand and draw a new hand as many times as you want during the draw step, but only until you run out of cards in your deck. (Rulebook p.6)

No — all cards you play stay in front of you for the rest of the combat and are only moved to the discard pile at the end of the combat. (Rulebook pp.6–7)

If you choose to stop and leave the Dungeon voluntarily, move the Boss token one step forward and then all players shuffle their discard piles back into their decks. (Rulebook pp.7–8)

If you cannot fully fulfill a required condition (like discarding two cards) the effect that depends on that condition won't happen, though you may still play the card and gain its basic power. (Rulebook p.10)

Unless stated otherwise, an enemy's effect remains active during all players' turns and updates immediately when game state changes. (Rulebook p.10)