Can I take back the applied subdivision modifier ?
That file has no more undo history, just a 1Million highpoly there.
That topology is just Subdivision Surfaced, no changed from it, so I think it can just reverse, but I don’t know how.
In Sculpting by Subdivision, I totally mistake in somewhere my flow, I never realized applying the modifier my model.
but, the modifier has been applied nightmarely. :_(
howa, thank you for giving me the clue of reconstructing Subdivision!
It works but it lose curent highpoly mesh(with vertexpaint) subdivision ;_(
It is destructive.
now, I get the highpoly and the copied lowpoly…
I can use shrink wrap to make a none polypaint lowpoly to subdvided high poly.
the last problem is vertexpaint.
Yeah, I don’t know anything about vertexpaint.
anyway, any clue is really helpful. thank you for telling me “un-subdivide” command 
Your welcome.
I’m not sure whether this is going to work or not, but maybe you can try Soft Mod
I got the news. I think I can do is just wait this.
https://twitter.com/pablodp606/status/1248974189924691969
anyway, thank you [Andrew_Ray]! I’m really glad giving any clue .
