Under MUTCD signal meanings, what is the key difference between a flashing yellow arrow and a flashing circular yellow?

1. A flashing yellow arrow applies only to the movement indicated by the arrow, while a flashing circular yellow applies to the approach subject to other controls
2. A flashing yellow arrow means stop, while a flashing circular yellow means go without caution
3. A flashing yellow arrow is for pedestrians only
4. A flashing circular yellow is the same as a steady red