the solution is not easy - and something all moderators in these forums would neither encourage doing or try to document.
It seems you want to start over, so consider these options:
1) if you are using the PVS, you can always extract a clean vm. Remember to delete the existing folder on your local system so you don't get confused as to which vm you should be using.
2) if you are using the online exercise environment, you can send an email to email@example.com and ask to have your online exercise environment reset. Given that this is the start of the weekend, you may not get a response until Monday.
Either of these options will give you a clean start.
Lastly, you could use your current environment and create a new applilcation using a slightly different name. The application name does not have to be HR Services - that was simply a naming convention we chose but you could also use "HRApps," "HRSystem," etc. The goal is to use a name that is meaningful and represents the application.
However, if you go with this last option, it is important to note that the "Background Check" exercise will not work as written. There is an import to do and it contains records with a context of SAE-HRServices-etc. The records would import, but you would not be able to access them from your app because the class paths are not the same. I honestly believe you would not miss any learning opportunity by skipping the background check import.