Understanding Desmond's Flashes [3x08]

Re-watching season 3 at the moment. If I recall correctly, we are to understand that the hatch implosion caused Desmond to become "unstuck in time," meaning that his consciousness can travel back and forth along his own history.

Most of these "flashes," whether of the future or past, end with his awareness returning to his present (that is, the show's present). Worth noting is that during these flashes, particularly the past flashbacks, he is frequently reminded of (or perhaps flashes to) his future. For reference, the time-travel of his consciousness is similar to how it works for Billy Pilgrim in Slaughterhouse-Five. So far, so good?

This is where it gets a bit confusing. What are we seeing when we watch one of his flashes to the past? Are they regular Lost-style flashbacks? Do they show how it happened the 'first time through,' before he ever failsafed? Another way of putting it: Was he always subject to flashes, throughout his life?

If not, if he did not have the power to flash before the hatch implosion, then we need a different interpretation.

Perhaps when he flashes back, his present-day consciousness returns to the past with some foreknowledge, basically creating a slightly different timeline. The first time through his life before the hatch, each of the flashback scenes we're shown transpired WITHOUT any strange pauses or weirdness for Desmond, as he had no foreknowledge. The second time through, caused by his consciousness going back and re-living the scenes, creates a second timeline where he has some foreknowledge.

For instance, in his original history before he ever arrived on the Island, he left his interview with Widmore, passed a busker playing Wonderwall, paid him no mind and continued storming home. But at some point after he failsafed, he had a flash where his consciousness traveled back to that moment, recognized Charlie, and had a conversation with him.

Do either of those interpretations work? What are we supposed to understand about his flashes?