Victims’ family members and rescue workers will have a week of free, 24-hour-a-day access to the long-delayed museum before it opens to the general public, for $24 per person, on May 21. About 8,000 unidentified remains will be moved to the memorial space this year, to be kept behind a wall inscribed with a line by the Roman poet Virgil: “No day shall erase you from the memory of time.”