Hear a crazy theory of mine..
Do you remember one thing Juliet said to Sawyer? She said to him: Let's go for coffee or smth like that. I think that she is going to say the exact same phrase when they will meet in the another reality ( the one in which flight 815 safely landed )
Now about your 2nd question, well really i have not an accurate explanation, but i think that it will be answered soon or later. :)
@Bscyb In this season there are no flashbacks or flashforwards, there are flashsideways ( which show us what would happen if flight 815 landed ).