Yes, Tetra is one of the princess' Zelda's (There are either 3 or 4 different zelda's depending on who you ask).
Tetras identity is revealed when the king of Hyrule fuses the 2 peices of the triforce
of wisdom together
Yup
Tetra
actually, from what I now from the game, tetra is, infact, Zelda. Its one of here disguises
You don't.
Defeat Belum and and save Tetra
Yes, because shes Tetra the Pirate!
Zelda does not appear in 2 games: Link's Awakening (DX) and Phantom Hourglass.In Phantom Hourglass, however Tetra is the alter ego of Princess Zelda, so you can still say that Princess Zelda did appear in this game, just in the form of Tetra. In Link's Awakening (DX) Zelda isn't even mentioned once.
I'm pretty sure she's Twelve. Zelda is always the same age as Link,and she is Zelda so...
Wind Waker
Zelda makes no apperace in Phantom Hourglass, exept under the name of 'tetra', the person your are aimed at saving.
Most likely you are referring to Tetra. Tetra is the leader of a band of pirates that sail the sea looking for rare treasures.
If you're referring to Phantom Hourglass, just complete the game and she will be restored.