Where do Reaper backups go?
All my project backup files are saved to a Backup folder in my project. Those are first class project, you could copy that to your root project folder and open, you will have a project the way it was then that file was created.
Does Reaper autosave?
A final thing to remember: this autosave feature requires one thing. It requires the project to have an initial save name and location. Basically, Reaper can allow you to start a new project without saving it anywhere. If you decide to do this, there is nowhere for it to autosave to and so your project will be lost.
How do I set up autosave in Reaper?
Yes arp_analog, there is, go to "Option/Preferences/Projects" and you can setup Autosave in a number of ways. Yes, you can find these settings at "Options -> Preferences -> Project" in the frame "Project saving". Additionally there are settings in "Options -> Preferences -> General" in the frame "Undo settings".