Praga Caput Regni

You generally take the wheel bonus immediately but it is legal to delay using that bonus until later in your turn; some wheel bonuses (like buying an egg) may be used after you earn the needed gold during the same turn (page 7).

No — if a red‑zone tile requires an immediate payment and you cannot pay it, you are not allowed to take that tile (page 7).

The special‑tile bonus applies only to the action you take from the action crane slot and does not apply to an extra action, but upgrade bonuses apply whenever you perform the upgraded action (including if you use it as your extra action); additionally, placing an upgrade can retroactively grant its bonus for that action if you already performed it earlier that turn (pages 9 and 14).

Placement of tiles with the Hunger Wall or Cathedral icon gives a sideways move (left on the Wall, right on the Cathedral); to move up you must pay 2 silver windows per upward move, and crossing tiers has an extra gold/stone cost; landing on spaces with points/arrows triggers their immediate effects (page 13).

Buildings with a cube claim a plaza; when a plaza is completed each player with a cube chooses one reward while the player with the most cubes takes both rewards; ties for most cubes are broken by comparing the total cost spent on those players' buildings (stone+gold), and if still tied all tied players get both rewards (page 11).

You may upgrade an action that is already upgraded, but upgrades are not cumulative: stack the new tile over the old and use only the new upgrade's effects; each upgrade still grants 1 or 2 advances on the Charles University track as printed (page 9).