This varies by manufacturer, please be more specific.
You are describing the mast.
Stays support the mast on a sailing boat running from the mast forward and aft. Shrouds also support the mast and run from the mast to the sides of the boat.
The mast.
IF you meant the 'mizzen mast' - in relation to sailing - it's the mast immediately aft (or behind) the main mast.
On a sailing ship, possibly on the mast.
A mast.
No, the mast is a vertical post that holds the sails on a sailing vessel.
On a sailing vessel having more than three mast, the mizzen mast is the third mast immediately aft of the main mast. It is a shorter mast than the foremast. It is often located over the stern of the boat or ship. Correction to the above: a "Yawl" or a "Ketch" has two masts -a mainmast and a mizzen, with the mizzen sometimes located right on the transom at the stern.
If a sailing ship has two masts, and the aft is shorter than the fore mast, then the aft mast is called a mizzen mast. And it is in english.
Barques, schooners, brigantines.
Yes, for night sailing.