Have an iPhone? Here's why you shouldn't close apps

There’s a Tutorial app? I have the Tips thing but it is pretty random and if I follow its link to Books to get the iPhone user guide (yeah, ok, there is OR RATHER WAS such a thing) I can download to Books the iOS guide for iOS 14.x.

My iPhone was acquired second hand and will not run anything later than iOS 12.5 (iPhone 6) so that iOS 14 guide will tell me all sorts of stuff about functions I do not have (and probably not about functions the later iOS no longer has).

This is the other thing I loathe about Apple. They seem to think that customers cease to exist if they have back-level hardware or software and refuse to offer (or even leave available online) support items for older stuff. I’ve looked online at Apple and there are old guides to iOS 5, 6 7 but not 12. I could find no iPhone 6 User Guide.