(1) If you are using an oAuth authid, you can only read/write to folders that you create with that id, so you can’t see folders that are already in your Google Drive. There might be a way around this, but somebody with more knowledge will need to advise how you would to that.
(3) To create a new folder on your google drive do this:
Duplicati.CommandLine.BackendTool.exe CREATEFOLDER googledrive://“My Test Folder” --authid=abc123xyz
(4) To list the contents of that folder you would do:
Duplicati.CommandLine.BackendTool.exe LIST googledrive://“My Test Folder” --authid=abc123xyz
As an additional note, although you can use Duplicati.CommandLine.BackendTool.exe to copy files from a local drive to google drive, you would need to do your own coding/scripting to check if files are new or modified before copying. I found rclone.org is an excellent sync tool which is a better choice (for me anyways) for copying files to google drive as it already has the ability to only copy new or modified files.