Can older iPhones (with iOS 11) display HEIF images?

Consider the scenario of restoring a backup taken on an HEIF/HEVC capable device (e.g. the iPhone 7 or newer) to an older device (e.g. an iPhone 6s, running iOS 11). Will images and videos taken on the new device and accessed on the old one be: - Not restored at all? - Restored, but not displayable (i.e. taking up space, accessible for sharing/uploading etc., but not shown in the gallery)? - Be fully compatible, and displayed/decoded in software? Is there a difference between images and videos? (I could imagine that images are decoded in software on older devices, for example.)