Is autosandboxing the same as Sandboxie?

Can I have Firefox start up sandboxed and have my OS be protected? What happens if I go on a malicious site this way?

no. You will need to make allowances for applications run with your browser.
Sandbox is not Sandboxie which was designed for this purpose.

Cheater87- Sandboxie makes provisions for allowing the user to establish pre-arranged computer resource file access for a browser’s bookmarks, passwords and such but the Comodo Sandbox does not so all of the browser’s files will be exactly the same when it comes out of the Comodo Sandbox as when it went in.