Under the Rules, when you have to wait for a passing train at a railway crossing that has no stop line (1.12), you must stop at the “No entry without stopping” sign (2.5). In this situation, the “STOP” sign is the second sign you come to on the road, so you must stop right before it. Stopping at this point ensures a safe distance from the train and good visibility.
Option 1. The first sign (1.3.1) only warns about a single-track railway and is not a place where you must stop. Option 3. The requirement to keep a distance from the rails (at a crossing without a barrier, at least 10 m from the nearest rail, not 5 m) applies only when there is no stop line, no “STOP” sign and no traffic light.