I had a very similar thing happen to me and one of my drawings I was working on for a while. I was finally finishing putting in all the permanent lines over the sketch lines, when out of nowhere, my laptop froze and became unresponsive. I force restarted it, but it never booted back up. Had to buy a new hard drive and lost all that progress. I know how that feels...very good work, though, bud.
i see your windows is in portuguese. do i hear a HUE?But seriously, really liked the animation
Save your source files on Dropbox. Revert to previous versions.
Stage 4 is the hardest one. Funny animation, I guess this relates to a lot of things: not just your Flash program crashing but maybe also a game crashing without you having saved the game. It might have been funny if you made the animation into a loop instead of ending it (again) at the beginning.
This is why I always auto save backups to cloud storage along with backups in at least 2 places on my computer very very very worth it, but I wouldn't be doing this if I didn't face this horrible trauma once before