[@Emma]

I can answer the first question for you, 
 you don't have to have more than one character some of us have multiple for plot purposes, relationship purposes etc. For me, I'm mostly going to focus writing on my main squeeze (Alice) but I have a side character (Sarah) that will pop in every now in then. Hope this helps :) 
As for the other questions, I'll let the others answer as it pertains more to lore