Galileo Galilei

You must spend at least one observation die of each color the Major Object requires, but you may spend any number of dice to meet the cost and any excess value is forfeited; return spent dice to the supply after use (page 6).

Yes — you may Observe up to two constellations in one action but resolve them one at a time; place your leftmost Constellation token on the chosen constellation, gain its listed rewards and then the reward from the space you removed the token from, and after you’ve used your seventh Constellation token you can no longer Observe constellations (page 7).

Comet tokens reduce an object's observation cost by their value and each can be used once per turn, moving/flipping as you use them, but they do not substitute for required colors — you still must spend at least one die of each required color (page 8).

You may spend Quadrant tokens to take free actions during your turn (not while resolving another action); costs are 1–4 Quadrant tokens and include options like changing a die color or +1 to a die (1), gaining a die or Write 3 (2), Persuade twice (3), or Spot a Comet (4) (page 9).

If you Persuaded any inquisitor (i.e., successfully moved a cellar inquisitor) during your turn, an interrogation happens in the Cleanup Phase: add the values of all inquisitors in your cellar and move your Tribunal token that many spaces (negative moves left); if you’re already at the track end you instead immediately lose or gain 2 victory points (page 12; cleanup reference page 10).

The game ends when the last Discovery card is placed on the Game Board; finish the round and give each player one final turn, then score University bonuses followed by Inquisition results (page 13), and ties are broken by highest sum of remaining observation dice, then most Quadrant tokens, otherwise the tied players share victory (page 13).