It's All Gone Horribly Wrong!

Well, not right now, but what do you do if it does? And what precautions can you take in case it does?

Note: This is about using Blender, not printing, which is a whole other level of horribly wrong!

Save

The first point is to save, and when you do something that could go horribly wrong, save first, and then savewith a different file name, and then do it!

Blender keeps a copy of your last save, with the extension "blend1". You can set it to keep more old versions in Edit - Preferences - Save & Load. Not something I have done, but it depends on your style of work.

Undo

The first thing to try is to Undo. Just hit [ctrl]-Z until you get back to where it was good.

Blender counts every selection or unselection as a step, and you can quickly get to the Undo limit. I would strongly suggest increasing it to 256. There is a memory limitation so if you hit problems, you may need to reduce it.

Go to Edit - Preferences - System to find the setting.

I have once gone back 256 times and got stuck, but that seems a reasonable number.

Recovery

Blender will autosave every so often, though it is not that obvious about it. If Blender crashes or your computer crashes, go to File - Recover - Auto Save... to see a list of recent saves,

By default, Blender autosaves every two minutes. You can alter that in Edit - Preferences - Save & Load, but that seems a pretty good number.

When it autosaves a previous one will get overwritten. This means if it does crash, you need to recover the file before you do anything else to ensure it does not get over-written.

The auto-save file is flagged as hidden so generally will not show up in your file manager. It is likely in C:\Users\[user]\AppData\Local\Temp\. Blender keeps a few of them, I found 18. But really, accessing via Blender is the best approach.