actually, from what I now from the game, tetra is, infact, Zelda.
Its one of here disguises
You don't.
I'm pretty sure she's Twelve. Zelda is always the same age as Link,and she is Zelda so...
Wind Waker
No, it isn't. It is only in Japanese and only available in the Japanese edition.
Yes, Tetra is one of the princess' Zelda's (There are either 3 or 4 different zelda's depending on who you ask).
Most likely you are referring to Tetra. Tetra is the leader of a band of pirates that sail the sea looking for rare treasures.
Go back to Windfall Island, and sneak into the bomb shop. They will be having a conversation, and they will give the answer you need.
Zelda, Princess of Hyrule (usually shortened to Princess Zelda) rules the Kingdom of Hyrule, and has appeared in every game to date with the exception of Phantom Hourglass, however Tetra, who appears in the game instead, is the alter ego of Princess Zelda. Zelda will usually be captured by Ganon (or Ganondorf, depending on the game) or another villain, whom Link must save from Evil's clutches. Zelda also has her own personal theme, "Zelda's lullaby".
According to the officials who created the Legend of Zelda series, and since Tetra is Zelda (sorry if you already didn't know), There are hints to such in the games. This is however assuming that All links and Zeldas are roughly the same in their reelings for one-another. Everything is implied, but not verified. Many people wish it was so, but there are so many other "Pairings" of Link and other people, that it would seem that the creators have left the emotional love life of Link and Zelda/Tetra/whoever up to the fans' imagination.
Yup
Tetra
You must travel into the fog and use the spirits' power to locate the ship and climb on to save Tetra.