Show Down is the final group in the single player Career and require 280 lights to unlock. Show Down consists entirely of races in which all of the opponents are bosses from earlier groups.
The "Keep your speed over 120 mph or more for an entire lap" demand does not require the 120 mph lap to start at the finish line. The lap can start anywhere as long as the player completes an entire lap without falling below 120 mph. This demand is easiest to fulfill at Event 2, SanFran Sausalito.