Sorry, missed this.
The Kierin was invented by the Japanese. They gamble heavily on it to this day. It's a mass-start sprint. The derny bike that paces them round serves a couple of purposes. First it offers the opportunity for them to jockey for position, which makes for interesting racing. It can get pretty rough, though I think the commissaires have got a bit stricter about the physical stuff in recent years. Second, it ensures that when the riders are released they are going pretty fast, so there is no chance of it turning into a slow, tactical affir.
As for the start positions, some like to be at the front and get first run when the derny bike pulls off, others like to come from behind. The latter strategy is more popular on 333 metre tracks where the longer straight gives you more chance of overtaking after the final bend.
As far as the inside line is concerned, I may be out of date about this. My recollection is that you can't race on the blue "out of bounds" area but that riders aren't penalised if they have to wander on there in the early stages. Someone might correct me about that.