Unfortunately no... I tried connecting my Bluetooth dongle and try to pair it up with my Android, and the USB interface only said that there wasn't a Storage Device connected. So the bluetooth isn't even recognized and thus it does not work with the receiver. Unless your bluetooth adapter works as a storage device, I don't see it working either.
yes it can be done. you will need a bluetooth receiver and will have to connect the output of the BT receiver to the Onkyo using RCA/Banana pins unless the BT receiver has a coaxial or optical out and then you will connect it to the respective inputs on your Onkyo. Doing this you will be able to stream music from your iphone. Typically a BT dongle will not work. The USB on the Onkyo is not intended for that purpose