RX2,TX2 in DUE via native USB port

To use RX1,TX1 we use Serial1.begin(), Serial1.read();
this is done via programming port

To use native USB port, we need to use SerialUSB.begin(),SerialUSB.read();

I need to use RX2,TX2 via native USB port. What should be the keyword for it? I tried Serial1USB , SerialUSB1. (Those are not defined keywords)

It's Serial2. It makes absolutely no difference whether you have your computer connected to your Due via the programming port or the native USB port.

Reference:
https://www.arduino.cc/reference/en/language/functions/communication/serial/