The Many Secrets of Bloodraven's Weir-Cave, Explained - A Song of Ice and Fire - Game of Thrones

Is Bloodraven really the three-eyed crow? Why have he and the children of the forest been watching for Bran? Why do the children even need human greenseers if they have their own? Will the white walkers invade the cave, and how will Bran leave? How far down do the tunnels go, and the underground river? All this and more!