It's the iOS app support that suffers. Apple makes it pretty unbearable to get apps for unsupported devices so I take those and relegate them to single use non-data holding devices like dashcams and other uses.
Oh that’s a bonus for me, I want her to use it basically for phone, imessage, and find my!
As of at least a couple of years ago, I could still redownload “the last compatible version” for my old iPad 1st gen (2010). I was able to download and run Netflix and Plex.
Yes, but you must have a nicer iPhone on the same iCloud account that downloads the current version, then you can use the "purchased" page on the old device.
Or for some apps that allow family sharing having someone in the family with a nicer iPhone also should work.