Chapter 1:
You need to ring all 3 bells that you encounter in the chapter and you will be able to go to the secret area after the snake fight.

Chapter 2:
You will have to talk to the drunken pig at the yellow-robed squire, which is located at the frightcliff shrine. You can go talk to him at this point, but you'll need the sobering stone which is located at the Windrest Bridge Keeper's Shrine - travel to the little town and it'll be on the left side. Give this item to the pig to sober him up. You'll then have to travel to the tiger palace and talk to him at the right side from the main entrance; give him the jade lotus. This item can be crafted and found in the water at the beginning of the map. You will then encounter him again at the frightcliff. For the event to trigger you need the Arhat Gold Piece, which you will obtain by beating the first prince.

Chapter 3:
Make sure you have the shrine at the Great Pagoda. You will have to backtravel here after having completed the secret area of chapter 5. The buddah will be waiting there and a cutscene will play infront of the middle, still empty, mural. If the first fight is too difficult for you, you can go back after getting all of Wukong's gear and getting the Skandha upgrade pill. It'll help a bit.

Chapter 4:
To unlock the secret area for Chapter 4, you'll need to defeat the Venom Daoist twice in two separate boss battles. The second fight is unlocked at the end of Chapter 4, so make your way through the story first before unlocking the Purple Cloud Mountain area. Fight 1:
-From the Upper Hollow shrine, go to the platform with spider sacs and look for a ledge that allows you to drop down.
-Cut through this tunnel while avoiding the enemies and the hostile spider sacs.
-At the very end, there's scaffolding leading to Middle Hollow (i.e. the main path). Instead of going down the scaffolding, go to the cliffside area/ledge.
-The Pool of Shattered Jade shrine is nearby. There's also a Meditation Spot here.
- Go and hit the big coccoon and the fight will trigger

Fight 2:
Eventually, you'll reach the Temple of Yellow Flowers. At the end of these long and winding paths, you'll arrive at the Court of Illumination shrine, which is right next to the arena of this chapter's boss. Instead of fighting this foe, turn around and you'll notice a tunnel.

Go all the way near the end until you reach another open area. To your left, there's a downward sloping path that leads to a dark cavern. That's where you'll find the Venom Daoist.

Chapter 5:

Follow the steps in this order:

Step 1: Defeat Pale-Axe Stalwart boss
Chapter 5 > Woods of Ember > Ashen Pass I: From this shrine go to the next corridor where a lot of bulls and undead soldiers are fighting. A miniboss will spawn here called “Pale-Axe Stalwart”. Defeat him, then talk to him until he repeats the same line of dialogue. He gives you the quest to find all Five Element Carts in Chapter 5.

Step 2: Defeat Crimson-Silver Cart (after Emerald Hall)
Chapter 5 > Furnace Valley > The Emerald Hall: Automatic story-related boss, unmissable, found on main path up the stairs after Emerald Hall. On the way to this cart you will automatically have to defeat two other carts “Brown-Iron Cart” & “Gray-Bronze Cart”. You can’t miss any of them, these 3 carts are all story bosses, beating them is mandatory to advance on the story path. If the Ox is there to join you in the fight, exhaust all dialogue with him afterward. If he’s not there, proceed to step 3.

Step 3: Talk to Pale-Axe Stalwart again at first location
Chapter 5 > Woods of Ember > Ashen Pass I: Return to where you first met the Ox, exhaust all dialogue. He will now move to the spot where you defeated the Crimson-Silver Cart after Emerald Hall. (If he’s no longer at the first spot proceed to Steps 4-6)

Step 4: Talk to Pale-Axe Stalwart where you defeated Crimson-Silver Cart (after Emerald Hall)
Return to where you defeated the third cart “Crimson-Silver Cart”. Pale-Axe Stalwart will be there. Exhaust all dialogue. (If he’s not there check his next location and first location again)

Step 5: Find the fourth Element Cart
Chapter 5 > Furnace Valley > Valley Entrance: From this shrine walk down the path, then enter the lava pool on the right. Go to the corner of the lava to find an Element Cart stuck in the lava, surrounded by a bunch of enemies (the cart won’t attack you). Interact with the cart to pull a string. Exhaust all dialogue with it.

Step 6: Find the fifth Element Cart “Rusty-Gold Cart”, talk to Pale-Axe Stalwart at his last location
Chapter 5 > Field of Fire > Fallen Furnace Crater: From Fallen Furnace Crater turn around, backtrack down the path where the big ball was rolling earlier on the way to this shrine. Halfway down the path, on the left, the rolling ball will have destroyed a barrier. You can now go down the left, follow that new path to reach Flint Vanguard boss. After him go down further until you reach the shrine “Cooling Slope”. After this you will see a big frozen gate. Go near it to spawn the final element cart “Rusty-Gold Cart”. It will injure the Ox NPC. After defeating the cart, talk to the wounded Ox NPC who will be sitting on the right side of the frozen gate. Afterward you can interact with the Frozen Gate, follow the linear path behind it until you get a cutscene that teleports you to the Secret Area “Bishui Cave”.

In case the little buddah doesn't spawn during your playthrough, make sure to get the Loong items and the skandha key items. I had them when going back to the mural temple, so it's here just in case.

Loong scales:
This item is obtainable after or during the first prince fight in chapter 2. To get it during, or if you have skipped the wandering villager boss fight in chapter 1, have the prince charge at you while you're standing infront of the blackened wall part and it'll open up a path. If you have beaten the prince, use your Wanderer spirit at the same part of the wall to crack it open. Collect the scales inside and you will be able to fight all the Loongs.

Chapter 1 loong:
At the part where you find the first bell, there is a water-fall, interact with it. You will need the scales from chapter 2 first.

Chapter 2:
At the shrine where you can access the drunken pig/secret area, you can to the top left of that part in the map and interact with the sand wall. There will be a spirit mini-boss infront of it.

Chapter 3:

When you get on the big turtle and have beaten the main story boss fight, go to the bottom left and there will be a bigger enemy sitting on a tree-log. Get close to him to trigger the fight.

Chapter 4:

You will encounter it on the green part of the cave, called: relief of the fallen loong. You most likely will have to fight this 1 after you have completed the first 3 because he mentiones them a bit in his cutscene but you might be able to trigger it without following the order. If it doesn't launch then go and beat them first.

Chapter 6:

Not necessary for the items to craft, but just beat it in case. After you get the cloud in this area, go immediately down from that angle, and there will be a round water place where the fight will take place.

Skandha (the monkey will be at each head):
Chapter 1 - forest of wolves, front hills. The head will be to the left after going through the narrow path. Go into the water and follow it to the head.
Chapter 2 - it'll be behind you when you're at the shrine for the loong fight in the big open area. You will have to collect 6 yellow buddah eyes to deliver it to the pile of rocks, beat it, and you'll receive the skandha.
Chapter 3 - valley of ecstacy, mindless cliff. Look down inside the hole and you'll see a tree, fall on it and follow the path to the top of that area you cannot reach from the shrine.
Chapter 4 - webbed hollow, purifying spring. You will see a lower part with a monkey on its head at 1 of the stairs.
Chapter 6 - beat the boss and the items will unlock. The entrance is the narrow place on the right side of the waterfall cavern. Go and craft it at Xu just to be safe at either the village if you have given medicine to the sick guy from chapter 3, otherwise Xu will still be at chapter 2.

*note. The first phase boss in the chapter 3 secret area calls out your Loong transformation while transforming into a tiger to snap you out of it, so it might be necessary to have the loongs up until loong 4. You can check after the loongs or the Skandhas if it is available for you. However, I had not completed the skandha boss and Loong 5 while going into chapter 3's secret area, but it might be still required to get the sequence to trigger at the end of the game.

Treasure hunter quest chapter 3. If the buddha doesn't spawn for you.
Step1
Forest of Felicity Keeper's Shrine;
- Follow the path that travels under the wooden gate that is near to the Forest of Felicity Keeper's Shrine.
- Continue along the path to pass under a second wooden gate.
- Continue along the path and stop just in front of a third wooden gate.
- Turn left, follow the downward slope, and pass under a fourth wooden gate.
- There are stairs just beyond the fourth gate, and the Towers of Karma Keeper's Shrine is at the bottom of them.

Step 2
Forest of Felicity Keeper's Shrine in the Valley of Ecstasy and follow these instructions to reach the Melon Field:
-Walk toward the wooden gate that is near to the Forest of Felicity Keeper's Shrine.
- Veer right just before reaching the gate and follow the slope downward.
- Go left when the slope runs into a large pillar, walk down the stairs, and continue descending.
- Cross the pool of water, turn left, and walk forward to reach an enemy that is standing near a cliff.
- Use the rocks and trees that extend from the side of the cliff to reach the Melon Field Keeper's Shrine.