NETGEAR ReadyNAS RN31200 "Kernel Panic"

1.  This is not Netgear support.  It is a community forum, though there is participation by Netgear moderators.  It you need Netgear support, go to my.netgear.com.

2. Your problem will not likely be fixed doing a USB recovery.  It is reporting an error mounting the root partition on the drives, not in the flash.  The OS for the NAS is on the drives, the flash only provides a boot loader and a means of putting the OS on the drives.

3. You are following the instructions for the wrong model NAS, and selecting an OS image that's not compatible with the procedure you are following nor your NAS.  Your NAS runs OS6.x.

If you have a backup of your data, your best bet is a factory default and restore from backup.

If you don't have a backup, then, given how little you seem to know about your NAS, I suggest you go directly to Netgear suport.  Doing the wrong thing could make your problem way worse.

If you choose to try something anyway, an OS re-install, following the instructions for your NAS, may fix it: How-do-I-access-the-boot-menu-on-my-ReadyNAS-102-202-212-or-312 .  This re-writes most of the OS on the drives from flash.  It also resets the admin password to the default (password) and changes IP assignment to DHCP, if you have changed it.  Don't accidently do a factory default (unless you are doing so because you have a backup, as in my first suggestion), as that will wipe your data.

But there is a chance that won't fix it, and you'll be needing Netgear support, anyway.