Good question. Its actually there is almost no difference between them because both show the past of something. But i will agree with Ewa and you need to know also that its used for unaccurate time that happened in the past.For example, i have gone to France. You dont mention the time exactlly when. And you say i went to France. Its the same meaning ;)

No because u talk about future and the second one is wrong ;) If you wanna use it in past tense it should be (we stayed until the rain stoped).