i think u should read the manual.

I think you should test drive.

yours is HU baru or HU lama.. ? if new one I cannot help you..
if it's old HU.. press the AUX button once again if you're in USB pendrive mode.. (make sure your phone are already playing mp3 songs and bluetooth on connected
with the HU)

AUX function will be USB, Mp3 Play (bluetooth streaming) and Ipod.. depends on either one is connected..

I'm not owning Forte of May onwards production.. I'm using old skool type HU 
perhaps you should wait for others to answer your question.

hmm... so far i am ok playing the songs from my iphone with 2 method for new HU:
a) connect the cable given and play the song in ipod mode.
b) pair the bluetooth with your car's bluetooth. all sounds from my phone will eventually came out from the car speaker i.e. ringtone, typing sound, mp3 etc etc.