YES HE DID YOU DIMWIT. Were you alive in the 80s? It often develops slowly, the brain is impaired long before absolutely distinct symptoms can be diagnosed. You have the disease (a spectrum of diseases actually) before it is diagnosed.
LOL, he is tweet feuding with celebrities at 3 am and has played more golf than any other President, unless you consider binge watching Fox News work, you are being delusional as usual.
No---he didn't and you have no way of knowing whether he had it 6 years before he was diagnosed. He did not exhibit any signs of not being able to make coherent decisions. This is just a made up story to try and down one of the greatest presidents in US history.
Impairment is a sliding scale and even his son wrote that he showed signs of a problem in 1984. He may still have been competent enough but he was affected. He was falling asleep all the time, that was very often in the news. He was however I believe a good natured man surrounded by people who cared and helped him. They also worked to preserve his legacy with denial of his condition. Guys like you would be better off back in the time of kings. People with dementia have good and bad days, even weeks.