I haven't saved my hard work, power failure! Is it possible to retrieve it from auto save or backup files?
Yes. Rename the files.
For example:
If the file name is Game.capx.backup1 then change it to Game.capx
If the file name is Game.capx.autosave then change it to Game.capx
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It's all covered in the manual.
Should be enough info for you but if not, just ask.