This instruction is still under development.
Please be aware of the possibility of not able to roll back your current stable releases, and operate with caution.
Open Terminal and type in the following commands,
$ eos-updater-ctl update $ pkexec eos-stage-ostree demo
and follow these steps to begin upgrading your Endless OS,
Open Terminal and type in the following command,
$ pkexec eos-rollback
then reboot your system, you should boot into the previous stable version.