What stage Alzheimer's does person not recognize grill from oven?

There is a short UTube video about how ALZ progresses in the brain. Find it by searching for Understand Alzheimer's Disease in 3 Minutes

On this site, there is an explanation of the stages here: https://www.agingcare.com/articles/Stages-of-Alzheimers-disease-118964.htm

That one observation -- not recognizing a particular object -- may not be enough to determine stage. Also, be aware that the stages apply to ALZ but not other kinds of dementia.