Hi,
A single cycle can take between 1 minute and several hours depending on what you want.
How much of what? See
www.sprpages.nl/downloads/faq
Yes, it is with all instruments/techniques: if you do it wrong it will report wrong answers
No, but a good basic foundation is always better.
How much time you will spend depends on what you want, you know and how far you will go to get nice and reliable results.
Also study
www.sprpages.nl/sensorgram-tutorial
Kind regards
Arnoud