The Bluetooth functionality we have not yet tested, because only a precaution system sold; but our 8 GB USB flash drive run poroblemlos; also works to control the steering wheel controls. (Once connected, the reading of the stick can vary depending on number of files take some time, give the part therefore necessary 1-2 minutes - we have not stopped).
Unfortunately, the car radio not permit random playback, so this consequently also applies to the "virtual" CD changer. I recommend, in advance at the manufacturer Dension (short googling) a Bilck throwing in the short installation and operating instructions. (Just this: CD1-CD4 control of the alphabetically first four folders, CD5 all files on the stick.)