You straighten a horizon, crop out a sign and send the result. Later, someone asks for the wider view. In Photos on Mac, edits made within the app can be reverted because Photos retains the original. But the file you already sent is a separate copy.
Choose the export, not a new edit
For the current edited appearance, select the picture and use File → Export → Export [number] Photos. Review the format and size options for the intended use. A small image for a message and a file for further editing are different deliverables.
For the imported source, use File → Export → Export Unmodified Original. You do not need to revert your edits first. An original Live Photo exports as a still image and a video file, so two files do not necessarily mean you selected two photos.
Make two clearly named destinations, such as “Edited for sharing” and “Originals”. Export one picture to each, then open both files outside Photos. Compare the crop, dimensions and file type. Similar names do not tell you which export option you used.
Reverting changes the library item
Image → Revert to Original removes the photo’s edits in the library. Use that when you actually want to change the library version, not merely obtain an original export. It does not replace copies previously emailed or saved elsewhere.
Before exporting hundreds of pictures, try a small selection with different edits and one Live Photo if relevant. Check the contents of the delivery folder, including whether the original reveals anything you cropped out of the version you meant to share.