1) WhatsApp goes on the device. You get it, not on the market or the WhatsApp website, but if you can find the installation file, you can easily get up and running it (of course, but only with one of the two numbers).
2) The phone can be used as a UMTS modem (under Windows at least).
3) The Exchange Untersützung is to synchronize contacts and appointments in the location.
In this respect, I am satisfied. A star I subtract because of battery life, while exceeding the modern smartphones by far, but still not nearly reached the promised values. I would love to have 10 euros more if paid for a more powerful battery would included.