Absolutely all of this. Each person has different symptoms, but they all seem to revolve around some WTF actions that just seem out of the norm. It much more than just memory lapses or forgetting why you walked into a room or what you were doing - it’s truly odd behavior.
As far as I know, there is no medical test for dementia or Parkinson’s, but they are diagnosed through clinical observation and physical “tests”, like those described above. It definitely sucked for my dad, who was in such good shape all his life, but during the last few years, could not lift a spoon to feed himself.
Another bit of advice is to closely monitor the caregiver (usually the spouse) and my mom in our situation. She had to do everything for my dad, feed him, get him dressed, shower him and she’s getting up there in age, so it really takes a toll on the caregiver. We finally decided that she needed help and got a series of nurses to help pretty much around the clock (after going the memory care route). If you’re financially able to swing that, I would advise that instead of the memory care home.