USB: 1 interface - one "device" or not?

Question

USB

There is a USB device, namely a smartphone. The device, by turning on USB debugging and other things, exposed USB interfaces in the amount of 6 pieces. I look in the device manager (View -> Devices by connection) and I see that the smartphone is visible only as 4 devices.
Another USB device (wireless receiver) exposes 2 interfaces and is seen as 2 devices. Something I do not understand anything about the connection between interfaces and devices ...
In this regard, questions: 1 interface should become (subject to the installation of drivers) one device? Or can more than one interface represent a single device? Well, a completely fantastic option: can one interface represent more than one device in Windows?
PS. Instead of Interface Association whether it, when 6 -> 4?

Answer 1

Yes, this is an Interface Association after all: several interfaces can be combined into one function.

Answer 2

USB routable interface - and you can connect to it a little less than 0xFFFF devices (endpoints)
When connected, the phone sends a descriptor describing all endpoints. To work with each endpoint, a separate driver is required that will process data for it.
The physical device is divided into several logical devices divided by function - debugging, storage, camera, modem. And inside the phone, each logical device is responsible for its own subprogram.

Answer 3

1 interface - 1 device. But no one bothers you to solder the hub directly to the board.