Can I use my phone as a Bluetooth transmitter?
Regarding this, can I use my phone as Bluetooth adapter?
No, that is not possible. The USB drivers for your phone do not permit that type of functionality. This is possible or not possible depending on what you want to do with the bluetooth.
Keeping this in consideration, how can I use my phone as a Bluetooth receiver?
Basically set up your Android device and plug in the cable to your stereo or headphones. Start the AirPlay/DLNA receiver. Then use the Twonky app to stream whatever is in your other Android device to the receiver. After setting it up Twonky should find your other device and let you stream to it.
Then plug in your Android smartphone using the USB cable. Open Settings > More > (under the Wireless and networks menu) Tethering and mobile hotspot and then select USB tethering. Congratulations, you have now successfully used your Android smartphone as a modem.