Does your suggestion imply a read-only disk drive and a read-only disk?
A bootable disc can NOT write to another medium unless you specifically instruct it to.
A bootable disc, by default, will not be allowed to write to any of your local drives, nor will it automatically write to a CD/DVD/BR disc due to the way the bootable disc is set up.
You can safely run a bootable Linux disc to try out the OS or several without the risk of it writing anything to your local machine in any way shape or form. If you encounter any problems all you needs do is reboot your machine and you can restart from exactly where you started from in the beginning.
‘Nix users, by default, do not allow anything to be written to any medium unless they specifically allow them to. You can boot the live distro, play with it, and then shutdown-eject-reboot whenever you wish and your base system will be untouched.
Simply remember that by default the running of the OS will of necessity be much slower launching from the bootable alternate drive instead of the default local hard drive, and take it from there.
Then play with it to your heart’s content. :)
Cheers!