I believe you need to have the
application submitted before Jan 1 if you are planning to satisfy the training reqt with an online course.
The VSP application should be adequate, but best to check the website for your local jurisdiction so you understand their intake process, which may have changed due to their COVID procedures.
As noted above, Arlington is a county, not a city. Cities in VA are independent and not in a county, even if they are surrounded by a county...so Arlington and Alexandria are two different jurisdictions. You definitely need to know in which you live to get the application submitted to the correct place. Assuming you are registered to vote at your current address, you can verify your county/city by looking up your polling place:
https://vote.elections.virginia.gov/VoterInformation/Lookup/pollingEither way, you need to get on this tomorrow because the circuit courts in both jurisdictions are closed Thursday and Friday this week.