No, there is currently no undo option to revert most changes made to a hosted feature service in ArcGIS Online Map Viewer and Map Viewer Classic. It is only possible to revert feature edits by pressing Ctrl + Z in Map Viewer, and clicking the Undo button in the Add Features pane in Map Viewer Classic. Alternatively, use one of the following workarounds to avoid saving the unwanted edits to the hosted feature service in ArcGIS Online:
Export the hosted feature service from My Content
In ArcGIS Online, export the hosted feature service from My Content to a local device as a backup data. Refer to How To: Back up content in ArcGIS Online for more information.
Use ArcGIS API for Python to download the hosted content in a file geodatabase format
In ArcGIS Online, use ArcGIS API for Python to back up the hosted content by looping through and downloading the hosted feature service in a file geodatabase format.
Create an independent copy of the hosted feature service
In ArcGIS Online, create an independent copy of the hosted feature service in My Content to allow making edits to the hosted feature service without changing the original item.