Faraday said Desmond in the front door of the Swan Hatch :

"You are the only person that can help us because the rules dont apply to him"

Ok I got it ... Desmond is special, unique

Then the question comes :

If the Desmond is the only that can help the LEFT BEHINDS why the O6 need to return to the Island to help them ?

I think he meant that Desmond is final piece in the overall puzzle. He's the only one that can save the O6 and the Sawyer/Juliet left-behinders together.

I took it as Daniel taken the initiative to try and save the group the only way he think will work. He has no idea that the O6 are trying to reunite to save them, so he's trying the Desmond can change stuff angle.

Desmond is the only one who can communicate between the two worlds. I don't think Daniel realizes just how important it is that Desmond get in touch with his mother since he doesn't know that the O6 are on their way in 3 years.

that's what I thought as well. But again, I dont know anything for sure.

that's what I thought as well. But again, I dont know anything for sure.

My thoughts exactly!

If rules don't apply to Desmond, and Faraday said the rules are that you can't get off the street to change what happened, then maybe Hawking was wrong and Desmond really can change things without course correction.

But why would the memory of this conversation with Faraday from before the 815 crash that actually took place in a time-jump after O6 left the Island come to Desmond in his sleep 3 years later? confused....

Remember the Constant He is the constant in both time frames. he is the means of communication like Faraday was in the previous episode.