You are not allowed to ask multiple questions according to enotes regulations, so I have edited your original question accordingly to focus on the resolution of this impressive short story. Let us remember that the resolution, otherwise known as the denouement, is when the problems that have been present in the story are resolved and the story ends. This is an interesting definition to think about, because personally I am unsure if the problems and conflicts that we are presented with in this story are actually resolved at the end.
However, having said this, to me the resolution comes after the climax, which is when Laura confronts the dead body of Mr. Scott. She experiences a kind of epiphany as she looks at his dead body, when she sees him as being "wonderful, beautiful" and in peace. As she looks at him, she also sees her own involvement in the garden party and "lace frocks" as being utterly unnecessary and frivolous. The resolution thus comes as she leaves the house in a rush, and meets her brother on the lane, and they have their final conversation which remains unfinished, but it is clear that they share an understanding of what Laura has experienced.