A:Answer Yes you can play "compatible" usb drives through this unit.
You can also record onto a usb drive, erase the usb drive, format the usb drive. I record from the cd, radio, Bluetooth, and a turntable that I have connected through the RCA inputs.
The unit has room for 1 cd at a time. But you could hook up an external cd unit as long as it meets the RCA specifications of the stereo.
The manual for my "CM4530" stereo states the following specs:
Aux In: 2.0 Vrms (1 kHz, 0 dB), 75 Ohm, RCA jack (L,R) x 1