In order to complete GW2 Bachelor of Secrets World 2 achievement you have to find every hidden room in World 2 Zone 2.
From the start to the Checkpoint 3
From the Checkpoint 3 to the Checkpoint 4
Hidden Room 1: Following the secret path toward the World 2 zone 2 shortcut, through a flower push, and a hidden cloud, keep climbing toward the upper part of that mountain. Place bomb between various tree branches and enter the hidden room 1.
Hidden Room 2: Just before the 4th checkpoint, with an assassin mini boss, turn left, where the frog is waiting for her victims. From the platform with frog, jump down, toward the rock plateau with a flower. Use this flower to push yourself toward the hole in the mountain. This is the entrance to the Hidden Room 2. You can buy Medium Health Bottle here.
From the Checkpoint 4 to the Checkpoint 7
From the Checkpoint 7 to the Checkpoint 8
Hidden Room 3: Right after the Checkpoint 7, there is a place where you can place your bomb. When bomb explodes it opens a hole to the Hidden Room 3.
Hidden Room 4: Do not leave this room yet, blow a hole with a bomb at the wall behind the shopkeeper. This opens an entrance to the balcony with a bauble, and it counts toward the Bachelor achievement.
From the Checkpoint 8 to the Checkpoint 9
Hidden Room 5: Under the building with gong, blow the wall with a bomb, in order to open entrance to the Hidden Room 5. Shopkeeper inside this room sells 400 bauble Chain Sticks. Nun-chucks that replace your ability number one is much stronger weapon.
From the Checkpoint 9 to the Checkpoint 10
Hidden Room 6, 7, 8 and 9: For these four hidden rooms, you have to climb on the roof’s top of a building after the Checkpoint 8. This allows you to jump on a rock plateau with a hole and a flower on it.
Path to the top of the building.
Jumping inside the hole, counts as one hidden room, and making a hole on the wall, and passing through it, toward the hidden chest, counts as another hidden room.
Hidden Room 6 and 7
Hidden Room 10 and 11
From the same platform where you have jumped into the hole, use flower to push yourself toward the mountain in the distance. Follow a path to the left, find a way through the maze of trees, toward the Raccoon Kingpin. You can place a bomb near the trees across the Raccoon Kingpin to make an entrance. Jumping inside the hole, takes you to the 8th hidden room. Use the flute that you can buy in the hidden Shopkeeper shop in the World 2 Zone 1, and play the combination written on the green pond. Combination is 332331. This opens hidden passage to the final hidden room.
From the Checkpoint 11 to the Checkpoint 13