Around what age do children learn that there are customs and rituals associated with death such as funerals, cremation, and cemeteries

I believe the correct answer is: around the age of 9.

At 9 years old, most children begin to understand that death is universal, final, irreversible, a nonfunctional state, and that there are customs and rituals associated with death such as funerals, cremation, and cemeteries. But, even though children reach this level of understanding, they continue to struggle with the idea that death is final.