Why does O'Brien never reveal the narrator's name?

At the end of the novel, the narrator returns to the police station to start his journey over. Why does the journey begin there and not in Mather's house or when the narrator meets Martin Finnucane?

Compare the narrator and Martin Finnucane. Are they, on some level, the same character?

Why are the policemen aghast that the narrator has no bicycle when he first arrives at the police station?

What is the significance of the narrator's wooden leg?

What is the significance of left and right in the novel? Note that the hidden road to eternity is on the left and that the narrator's left leg is wooden. Sergeant Pluck says that Policeman Fox is searching for a road that leads to the right, and the narrator takes the right-hand road to finally return to his...