Programming Arduino

Good evening

I have a question on programming Arduino with boot loader.

Is it possible to program using the second serial, as for example Arduino Mega, like the serial connected with the usb converter? In this case I think I have to use Rs232/Usb converter to connect Arduino to the Ide in the pc.

And is possible to read whit the Usb the program installed in Arduino?

Thank's a lot.

And is possible to read whit the Usb the program installed in Arduino?

As a hex file, yes. As code, no.

Is it possible to program using the second serial, as for example Arduino Mega, like the serial connected with the usb converter?

If you rewrite the bootloader, yes. Using the standard bootloader, no.