With CS6 one has to be very careful and should have a base knowledge of how the program treats files. For instance if you don't save a file under a new name straight away and start to make changes with the menus at the top of the program window, you can easily degrade your file andnot get the original pixels back. CS6 is designed to use layers to alter the image appearance. That is where temporary changes can be made first.
Huh?
I've opened tons of my RAWs in CS6 and done quite a bit of correction before first saving (and it defaults to saving as a PSD). I would need to put in deliberate effort to modify my RAWs (using save-as). It did make XML files to save my RAW corrections, but the RAWs themselves are unmodified.
As mentioned: the alternative software is GIMP, which is free. It will do much of what you are after, and is what I used until I had saved up for PS.
