Mobile Safari updates for older iOS versions I am aware that Safari for iOS is updated whenever iOS is updated.

For devices that cannot update to iOS 11:


Can the Safari on those devices ever be update to recent versions (outside of the iOS upgrade)?
Does the Safari for those devices receive any updates at all (e.g. security)?
No. Safari only updates with iOS releases. If there is a very serious security concern Apple might release another (iOS) update to a previous version, that adds security fixes to Safari, but never Safari by itself, and no new features.

On MacOS however you can still download Safari updates for newer OSs.