No, the demo version is the full software, except for the watermark and the inability to download presets.
As far as audio and adding clips is concerned, are you trying to use the software like an NLE (such as the basic WMM or something like iMovie or Vegas)? If that's the case, the FXHome programs are not meant for that kind of work, but rather to enhance and add to your shots. You should be able to add a clip though by importing, dragging to the timeline and then positioning it with your mouse. Have you tried that yet?
For sound help when rendering, check out this tutorial.
And, be aware that sound does not play back within the program.
Hope that helps