Help me reset the terminal after sudo command mistake
In step 2 you copied the original hosts file to a backup location at ~/Documents/hosts-backup (i.e. in your documents folder).

All you should need to do is rename that file to hosts and then copy it to /private/etc/hosts (overwriting the edited file) to undo any damage that you may have done.

However if you only got to Step 3 you may not even have edited the file yet - in which case a reboot should be sufficient.