As you can see from the photo, there is no command and I did not root my phone, I used it as I received it

In fact, I don't have a recovery image but in a general extend, I do not have a recovery mode. When I apply the method to access it, I can only get the page with a small android with message saying "no command". So I cannot wipe. And as I can't enter my phone except in guest mode, I cannot...

No, I didn't. 

I have combined problems, but the first one is definitely the pin changing by itself. The next is that I can't wipe the system, because my phone does not include a recovery image... Then I'm blocked, I'm not even sure to be able to do an update if a new version is coming out...