Lite version includes only Loudness and spectrogram outputs, while full version also provides beats, average frequency, chromagram and more customization.

Addon should work with .mp3, .wav, .ogg and .flac. Sometimes different versions of these formats may not be compatible, in that case use a tool like Audacity to convert your audio.

Yes, the addon only contains nodes with audio information. Don't worry, they are fun once you figure them out.

Yes, that can be done by going inside one of Sound Nodes node groups, right-clicking on a desired value and choosing "Copy Driver". To animate a differnt property, right-click on it and choose "Paste Driver." 

Special nodes for Geometry Nodes and a tool for analyzing music.