Is there an application that allows you to add a virtualized version of your operating system into the mbr? By virtualized, I mean that if you boot this one, any changes made in it will not be committed to the disk. Just like how deepfreeze, returnil, and shadow user works. Is it possible to do that? Because the applications mentioned above requires you to reboot if you want that changes will not be retained.
Do you mean something like VirtualBox or something that you can choose from at boot through a boot loader like GRUB?
If you are wanting the latter, than you could install your OS on a USB stick and then boot from that, then the changes will only exist on the USB stick.
Hope this helps!