How to decompile a build?

And how work backup?

There certainly are ways to decompile Unity projects, just as you can decompile almost anything else. But it's not a simple process where you can just click "decompile" and get back exactly what you had. Use Google if you want to find out more.

Backups "work" by taking regular copies of any works-in-progress as you create them. Then, when you make a mistake, you load one of your old versions to recover from your error. If you haven't already been taking backups or using source control, there's nothing you can do about it now except learn from your mistake....

Ok... Thanks :)

Sure, you can hex edit anything... but that wasnt what he was asking :)

Simplest form of backup is just to make a zip of your project every time you get something working and store it somewhere.

If you are using Apple you SHOULD be using time machine, and you can recover lost files from there if they arent too old.

Also, online storages are great - just don't rely on them too much. Dropbox once replaced my current project with a two week older project automatically (without any of my interaction with DropBox). So, always keep physical backups, not just online! Time$$anonymous$$achine is a huge lifesaver.