1. The car had hardly stopped . two policemen came to it.

2. The children had hardly entered the castle when they were shocked by the ghost.

3. The rain had hardly stopped when the rainbow appeared at that moment

Hardly only the car has stopped, two policemen have approached to it
2 children hadn't time to enter into the lock as they have been shocked by reduction
3 hardly the rain has stopped, as there and then there was a rainbow