You are looking for an “offline” mode, not a “demo” mode. That being said, there is no “offline” mode currently available on the CQ. This has already been requested multiple times on this forum. For example, Real Offline-Mode for CQ (as for SQ)
A demo mode usually means the console is fixed and not editable and the system acts as if there is audio going through it when in fact there is not. It shows you what the system might look like when being used (ie active meters, gate and compression indicators, etc) but doesn’t actually allow a person to modify the settings at all.
An offline mode is one where there is no audio passing through they system and the system correctly reflects a “no audio” state (no active meters, gates, compression, etc). However the various settings can be changed/modified and saved for future use.