>First step: Album Mix
Second step: Headbanger's Mix, made by remixing the original album elements (and adding a few new bits)
Third step: single version, made by editing the Headbanger's Mix (rather than re-mixing the original album elements)

I will disagree with you. Name "Headbanger's Mix Edit" sounds much more like mistake/misprint for me.

Headbanger's Mix includes new instuumental parts form another take (that's why they're sounds a little bit unnatural in old-and-new docking parts).

Single mix doesn't includes any of new parts from Headbanger's Mix, but it includes new mixing of vocal & guitar on 'Baby now your struggles all in vain' verse. So the single version is completely new, unique mix which doesn't related with Headbanger's Mix.