Extract the outer exercise pack first. Upload its source.zip into ZIP preview and extraction: expect three non-directory files. Export all selected as ZIP, then reupload extracted-files.zip and compare every full path, byte count and content. For a north subset uncheck south/report.csv, retain north/report.csv plus notes.txt and label the two-file output partial. Download the north and south CSV individually: both suggest report.csv; verify N01/100 versus S01/250, then save explicit source names using download-map.csv. case-conflict.zip contains North/report.csv and north/report.csv; it should stop with a case conflict and disable selected-ZIP export. Reupload source.zip to recover three paths. Compare individual file checksums, not whole repacked ZIP bytes. This exercise does not establish malware detection or upstream completeness.
