What does an octagonal red sign with the word 'STOP' in white letters mandate?

1. The driver must bring the vehicle to a complete, full stop before the stop line and yield right of way to all traffic on the intersecting road
2. The driver should slow down and proceed without stopping if no cross traffic is immediately visible
3. The driver must stop only if turning left into the cross street
4. The driver has priority over cross traffic after pausing momentarily