The demo has been updated a few times in the few days since release. Here's what's changed:
Bugfixes:
Patched the ability to walk on water using Brynn or a rock (also polished up the splash animation)
Patched the ability to interact and fall through a platform (Z+down) at the same time
Fixed non-functioning Flower Isle teleporter
Fixed softlock when pausing on the title screen and selecting "Load Game"
Fixed action instructions ("Press Z on the enemy!") fading out immediately
Other changes:
Defeating Cycloneclops now gets rid of the lightning in Flower Isle (my brother's suggestion)
Partner characters don't bumble off ledges as easily
Partners and NPCs have audible footsteps