eM Client Backup Routine

I often use eM Client to give me a local backup even though I use other clients to access my email. I have set my PC (Win 10) eM Client application so that it backs up every two days. If I haven’t started the application on my PC, would it first sync before it backs up?

No, it would not sync with the server first. The backup is essentially a separate application that compresses the database folder to a zip file, whether the application is running or not.