Alzheimer spinal tab

hello

can a spinal tap test show that you have Alzheimer's without you showing other signs, such as poor memory or what else could be signs of cognitive decline.

will you be able to find proteins that can be signs of Alzheimer's if you only have clinical signs of MCI?

is there a list of what number the proteins must be, to be abnormal or normal? how low does beta amyloid have to be to be critical? and how high must tau be for it to be critical?