This video-walkthrough covers all puzzles and achievements:

Oasis
Go through the first portal.


Returning
Find the way out of the ice cavern.


Nimbo
Complete the prologue.

Lapso
Three is enough.



At the beginning, turn around and walk in the wrong direction three times:





Curious
Curiosity killed no one.



You have to find three secret areas and perform two special actions:

1. Find the spider area.
   
2. Find the dark corner inside the cave behind the waterfall.
   
3. Find the ice cave.
   
4. Shake the flesh cube [Beating Achievement].
   
5. Step on a pool.

Spider Area (first cave area; on a plateau on the left):





Dark corner (third cave area; stay on the left and find a dark dead end in a secret area):





Ice cave (stay on the right after entering the ice area):



Flesh cube:



Pool:






Beating
It will remember that.



Shake the flesh cube in the last area: