Some type of net access is required to download clips from the NCH clipart or sound effect libraries and, rarely, when prompted to fetch a codec or related program.
Otherwise, if source files are available, there should be no impediment to creating a project without being connected.
Of course. Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. Then you can restore a project to the state it was in when saved. Just double-click the VPJ file (which isn't playable).