No problem according to Dell: http://www.dell.com/support...
The XPS 13 is even supported in the 9350 version, i.e. the predecessor of the 9360. According to the description, all compatible devices are also charged.
No, unfortunately this is not possible. The RAM is soldered onto the mainboard (See specifications: Onboard) and cannot be extended, as there are no additional memory slots. If you want 16GB of RAM for this Laptop, you have to buy directly the appropriate model. On Dell's Webstore you can usually adjust the product to fit your needs (not possible at Digitec).
You can have almost any product delivered to the shops if you like to pick em up (Select the option at checkout). Show-Room indicates just that some products are on display and can be examined/touched/tested.
Yes, it's QWERTZ in Swiss layout, as usual.
It's Windows 10 Home. You can choose during installation or change/download the language after installation at any time.