Istanbul: Big Box

You must either pick up an Assistant or leave one behind when you end your movement to be able to carry out the Place action; if you neither pick up nor leave an Assistant your turn ends immediately (the Fountain is an exception). (p.8; Fountain exception: p.18)

After movement (and after you pick up/leave an Assistant) you must pay each other Merchant 2 Lira in the Encounters phase before taking the Place action; if you cannot or choose not to pay, your turn ends immediately (you don’t have to pay at the Fountain). (p.8; Fountain exception: p.18)

When you free your Family member from the Police Station you send them to another Place and then immediately carry out that Place’s action; your Family member does not suffer encounters and you do not have to pay 2 Lira (and you may not use the Governor). (p.19)

Yes: after you pay the goods and receive the Mosque tile, you immediately add your 5th Assistant to the bottom of your Merchant stack (the 5th Assistant is kept nearby during setup). (p.19; setup note: p.7)

In the base game a player collecting 5 Rubies triggers the end (finish the round), but in a 2‑player game and when playing with certain included expansions the end condition becomes 6 Rubies; with the Letters & Seals expansion the game ends when a player has 6 Rubies. (p.8; Letters/expansion note: p.16)

You send all caught Family members to the Police Station and, for each one, you may take either 1 Bonus card or 3 Lira from the supply (you get no reward if the Family member was already in the Police Station). (p.9; Police Station details: p.19)