a tough question

1.Lying on the couch, the boy fell asleep
2.The boy fell asleep, lying on the couch
3.The boy fell asleep lying on the couch

are they all correct?
How to fix them?

Number 1 is correct.  You need the comma and you also need a period at the end.

Number 2 is correct.  You might or might not need the comma (depending who you ask, I've had teachers tell me both are correct) and you also need a period at the end.  In this case, I don't think the comma is required.

Number 3 is the same as number 2 without the comma.