Hi nikeb,
What exactly do you mean by "lose my json connection"? VC does not actually maintain a connection with Kodi except for events that are received from Kodi. When you give a voice command that tells Kodi what to do, a new connection is created each time.
Yes, the full restart action is disabled in the demo version to try to prevent abuse. I'm not sure about the quick restart but it would not solve your problem anyway.