Two Questions:
1. When Sleep by Hypnosis or sleep powder, what % chance of my pokemon waking up next turn?
- I heard they can be asleep for 4 turns, then they wake up?
2.When My pokemon asleep, and I return it, and release 4 turns later, do they wake up? similar to question on top
-What about Rest? also
Try to look higher in this page. TheMaskedNitpicker did a good job answering similar questions regarding sleep.
To sum up, your pokemon when being hit by a sleeping move has a sleep counter on it, which goes down everytime your pokemon is using a turn sleeping or sleep talking or snoring if anyone uses that. Switching out won't make your counter go down, but it will not reset it either, which means that if you were supposed to wake up the following turn, you still will when the said sleeping pokemon is back and decides to do something instead of switching.