A portion of a story, if I can loosely call it that, was how I initially started writing. My very first draft was characters and a conflict. During the writing of it, I realized I needed to hammer down character motivations, and thus version two was born.
As I wrote version two I realized that I had an ending in mind that no longer fit the draft that I was writing. I scratched the entire beginning of the story aside from a few key points, started in the middle of things, and worked my way to an ending that made more sense.
My third draft is technically my finished manuscript. It's the only version that goes from beginning to end, has fully developed world building, and proper motivations. The problem is that when I finally finished it (as you said) the beginning no longer fit the ending. The version I have on Tapas is meant to rectify that. The beginning is newly created, but the major turning points from the most finalized draft are all the same.
Mind you, this was a three year process, lol. I'm a very messy drafter and my characters tend to bully me, so I've always seen myself as more of a character writer than anything else.