Apple has taken care of quite old hardware as well as updates for current devices. But only in one point.

ios 9.3.6

Some of the listed devices are eight years old, yet Apple provides them with an update. However, it seems to be less a security update than an error correction for GPS positioning as Apple writes here.

In order to correct this circumstance there is an update for the old devices. For devices with iOS 10 the current version is now 10.3.4, for devices running only iOS 9 it is 9.3.6.