Why do pirate ships have three masts?
If the ships wheel turns port does the ship go left?
Yes, if the ship is underway and the rudder works.
What was the name for the one ship that was allowed to enter a Japanese port to trade each year?
During the Edo period, it is rumoured that the so-called "Black Ship" was the only ship allowed to make fast at Yokohama. It was the treasure galleon making the 3-point route to Portuguese-owned Goa and then back to the new world, typically moving silks and precious metals.
This information is apocryphal. James Clavell covers it with some literary license in "Shogun"