It depends on your interests and schedule. If you want to soak up everything, three days might be ideal.
It really depends. If you just want to browse and catch a few highlights, one day could be enough. But for a more immersive experience, I'd say at least two days.
Well, it varies. Some people enjoy a full weekend, so two days. But if you're a hardcore fan and want to attend all the panels and events, maybe even four days.