Hard. Hard to tell without a clinical examination and it depends on whether it was lanced or packed with gauze or surgically removed and/or given an antibiotic, etc. Read more about boils and treatment options at the link below. I hope that helps a little.
5-10. 5-10 days if no complications arise (infection, necrosis of the edges, etc).
Depends. Depends on size and severity of infection. Could take several days to several weeks.