Use the control panel to back up your data. You can also schedule backups to run at set times ($0,10 per GB).
Yes, you will be charged for backups ($0,10 per GB) based on actual usage at the end of the month.
No, you can’t download backups. You can only restore a VPS to an earlier state using standard backups from the control panel.
Yes it is possible to rebuild your server. When you manage your server you need to select the "destroy" tab. In this tab it is also possible to "rebuild" your server.