There’s no iOS backup feature.
Yeah, I hear your scoff, but iCloud Backup is not Backup. It’s a system clone. If you delete Contacts accidentally, you can’t readily restore Contacts of, say, 3 days before. When my sister accidentally deleted most of her contacts she had no way to restore them from iCloud. -Gordon's Tech
I kinda disagree with this. It's true that there's no way to partially restore an iOS device, or in other words restore a file you deleted from your device.
But in this case it isn't iOS that lacks a good versioning strategy, but it's iCloud.
When I accidentally delete a file from my Dropbox account, Dropbox allows me to restore that file if this happened within the last 30 days. But if you delete anything on iCloud it's gone. Time Machine on the Mac solves this issue on OS X but on Mobile there no such thing as a file backup of cloud files.
So what's missing in Apple's iCloud is a versioning and backup strategy. It's what makes me hesitate switching to iCloud Drive for all my files, and there's no way I'm going to trust them as the keeper of my photos. If you store data you need a backup strategy. Which means multiple independent copies of your data on separate locations and an easy and reliable way to move data between these locations to recover lost data.