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.