Christ's Active Obedience

How and why did Christ become righteousness by earning it in the body prepared for Him. What does it mean that Christ 'bore' the sin of His chosen ones? How do we see Christ as the connection between the sinners He came to save and a Just God? Why did God need a Savior? Does Christ repent for His chosen ones? Does Christ believe for His chosen ones? Why must any attempt at obedience be eternal? What is active obedience?