Where's the third time flute?

[Mew Supporter!]

Have got the one:

from whatizname (Mt. Battle 1st leader)

and UFO disk U.

Where's the third?

Edit: Also, how do I trade with the gameboy?

 

[Neko Godot]

Beat Mt. Battle in story mode.
You can trade after you beat the game.

 

[Mew Supporter!]

And the time flute?

 

[hikari_blaze]

Beat Mt. Battle in story mode.

She just said it.

 

[Mew Supporter!]

Oh...

And by trading, where do you trade? In a pokemon center?

 

[Latios Trainer]

yea the phenac city pokemon center's basment

 

[The Great Butler]

More specifically, the third Time Flute is at Mt. Battle's summit--you are NOT given it for winning the 100th battle. There is a chest to the right of where you come up from platform 99's stairs that you must open to get it.

 

[Blazichu]

Find the chest holding the third time flute on the top of Mt.battle