The third level from the full game has now been added to the demo in time for Next Fest. It had always been the intention to have three of the seven levels in the demo but I wanted to give do another pass over it to remove a couple of placeholders.
The game autosaves every time you hit the button to end a level, and while there was a hard compatibility break from v1.00 to v1.01, any saves made in level two on v1.01 can safely be loaded in v1.02 and all you have to do is hit the end level button again and you can immediately play the third level.
It's unlikely that there will be further changes to these three levels before release, and saves between the demo and the final version will be fully inter-compatible so provided there are no compatibility breaks you'll be able to load saves made in the demo within the full game and continue where you left off.