Take a look at PHImageRequestOptionsVersion
PHImageRequestOptionsVersionCurrent
Request the most recent version of the image asset (the one that reflects all edits).
The resulting image is the rendered output from all previously made adjustments.
PHImageRequestOptionsVersionUnadjusted
Request a version of the image asset without adjustments.
If the asset has been edited, the resulting image reflects the state of the asset before any edits were performed.
PHImageRequestOptionsVersionOriginal
Request the original, highest-fidelity version of the image asset. The
resulting image is originally captured or imported version of the
asset, regardless of any edits made.
If you ask user before retrieving assets, you know which version user specified. If you get a phasset from elsewhere, you can do a revertAssetContentToOriginal to get the original asset. And PHAsset has modificationDate and creationDate properties, you can use this to tell if a PHAsset is modified.