Questions on past perfect

1. What is the difference?

Before they had gone up to the second floor, they fell.

They had fallen before they went (up?) to the second floor.

2. I think the two are similar in that the past pefect tense kind of does the work of the present perfect tense. What do you think?

a.His son's wedding was the happiest moment he had ever experienced.

b. His son's wedding is thehappiest moment he has ever experienced.

I think this is similar to the "a" sentence.

His son's wedding picture was the most beautiful picture he had ever seen.