I had to load up a save to get this, so here we go:

A. "With the vale at your back, go forty-nine.
Then seven to the right on the truest line."

Follow the instructions, and it leads you to another spike which points you to the next clue:

"With me at you back, go twenty, then twenty to the right."

A piece of broken machina says: "Right sixteen and right four."

The circle on the ground will say, "Continue on. Find me."

Going to the circle near the thorn will give you the final clue.

"The password is... GODHAND."

This references the password system in the airship, unlocking the location of Rikku's celestial weapon, Godhand.

Q. There are a total of three ways in the game to obtain dark matter. What are they?