"I could be wrong, but I think most of it ends up being modifications to existing codes, so I'm not sure how you would undo all of that."
Kevin, do you even read what you are writing before sending own posts? How dumb would have to be any developer to not keep the backup of working/previous/last of version of the software he is writing? Seriously, I had to read twice your post to believe you wrote it.
First on PMDG forums, now here. Your posts are usually useless, contributing nothing to the discussion and you often act like a press spokesman for companies. Let alone the fact that sometimes you try to answer in the style of being a developer yourself. Please, STOP!
Umberto, forgive me but I had to finally rise the voice about this. It's too much and I'm not the only one seeing this like that.
As for the topic itself, @quentcor, I agree with you that there should be backup and possibility to download older but working properly version of the software.
However, I highly disagree that you should be even thinking about paying anything extra for that. This simply isn't right.