USB: yes, simply connect a USB drive and select usbdiskX as the target when configuring the backup.
offsite service: as far as i remember only to another Terastation or Linkstation offsite, go to system - backup - view NAS devices. there should be something called “Off Subnet TeraStation" - just add the (public) IP. You will, of course, need to configure the routing, ports are TCP 22939 and 873 / 8873 (encrypted)
I don't think this one had Amazon S3 or dropbox yet.
That is with stock firmware, of course. If you switch it over to Debian you can do pretty much anything you want if you are comfortable enough with it. 1000001101000 has done some nice work on this, see
https://github.com/1000001101000/Debian_on_Buffalo