I dream a dream we done in one take (well dicumented) There are no more versions. The trailer was just a cut of the sound over other scenes
No, there were multiple takes of it. By 'done in one take' what is meant is that Anne started the scene and the camera kept running until she finished the song - there were no breaks, it wasn't different takes of different bits of the song put together. The remarkable thing was that the song is so long, and wasn't cut down unlike some of the others.
They probably used the first take - they did that for some of the others. But there is no chance that thy only filmed it once, if only because they'd need back-ups in case something went wrong with the take they planned to use.