You can only revert a machine after you have started that machine.
The command to revert is located on the far right of the challenge machine row. To revert a machine, use the command immediately to the right of the start command.
Warning: Reverting a target machine will return it to its original state, and any changes you have made will be lost permanently. This action cannot be undone.
Please ensure that you have saved all of your work before proceeding and fully understand that this process is irreversible.