How to make the iPhone elderly friendly?

You can change the Home button behavior a little under Settings>General<Accessibility>Home-click Speed. You may want to look at other Accessibility options while you're there. The Zoom feature may be useful.

To the best of my knowledge, there's no way to completely disable the Notification and Control centers. Or to lock WiFi and BT on.

I've spent a lot of time as part of my job teaching older folks how to use smart phones (a couple of my students were in their early 90s). I've discovered the most important thing is to reasuure them that, as long as they don't drop the phone in water or bash it with a hammer, they are probably not going to hurt it. Often they also seem uncomfortable feeling or appearing "stupid". So, I also tell them that all those little kids who seem to understand technology from birth aren't smarter than they are. They are just not afraid to push the buttons and see what happens. My sense is that the fear that something bad will happen drives out any sense of playful exploration. Sometimes, if I can get them to start playing an little, they relax. But it is a challenge.

You may also want to get them a cheap stylus. That seems to make many people more comfortable.

Best of luck.

There are other devices I would probably have recommend for someone with Alzheimer's. Those folks definitely have difficulty learning new things.I probably would have gone with, at most, a basic phone and a carrier's service for tracking/monitoring phones on the account. Verizon calls their version "Family Base". An iPhone is going to be a challenge. Having WiFi on does improve location services accuracy. BT doesn't really matter for that. I wish I had some better suggestions.

Best of luck.

Shoot, I accidentally call up voice and Siri all the time. It is kind of annoying. The stylus is a good idea. It makes hitting what ever stuff they need easier.