Kickstarter Original Computer Kit


I have a Kano Kickstarter Original Computer Kit with a Raspberry Pi Model B Rev 2.
I run an “apt-get update ; apt-get upgrade ; apt-get dist-upgrade” with success, but now it does not boot and shows the following message:

Sorry! This version of Kano OS requires a Raspberry Pi 2 or later.
Don’t worry. You can get a version optimized for your computer.
Head to and grab Kano OS 2.1

Is there a way to downgrade the OS without reinstalling?
If I reflash the sdcard, how can I guarantee it will not upgrade again to an incompatible OS version?