Comunication problems with Arduino M0 Pro

Hi.

I bought my first Arduino (M0 Pro) two weeks ago and, because this board is quite new, I'm having several problems using serial communications due the lack of documentation. I have three main problems that someone can probably help me (please note that I'm a amator concerning electronics):

1) My biggest problem is to retrieve data from the arduino to the computer (even using a simple "Hello World" sketch) using recent Visual Basic .NET. When I use the IDE, I receive the messages without problems. However, when I use a program to read the data using Visual Basic (e.g. http://www.martyncurrey.com/arduino-and-visual-basic-part-1-receiving-data-from-the-arduino/) the program is not able to get any data. I also tried the program TERMITE 3.2 (http://www.compuphase.com/software_termite.htm) and the result was the same. Meanwhile, I manage to test these programs in a Arduino UNO, and both the Visual Basic and TERMITE programs worked fine. Is there any issue concerning the Arduino M0 Pro and the communications with a computer that I don't know?

2) I have a sensor that communicates by RS232 that I would like to connect to the Arduino M0 Pro. I tried to plug it to ports 0 and 1 but, apparently, didn't work. I also tried to use the available native USB port, but I could not understand how to do it, since the available information is very limited. Can someone give me a suggestion.

3) This is a basic question that, probably explain my last problem: what is the difference between using in the sketch: Serial, SerialUSB and Serial5. I see people using these keywords with the Arduino M0 Pro, but is not obvious when and why they are applied.

Thanks for reading this message,

CB