OLD Passports….To upload or Not?
You need to list EVERY international travel in the "last 10 years" or from the age of 18 (whichever is later) regardless of the period of stay and regardless of whether you have a visa or stamp or marking on your passport.
You may skip travel between country of residence and home country, but do indicate about this in your LOE.
You however need to upload ONLY your current valid passport. You do NOT need to upload your old passports regardless of the visa stamps.
CIC is not checking your copying/listing skills. These details are required to establish your personal history, your PCC requirements, Criminality and background checks.