Unfortunately, I don't find the kettle very practical. The digital display is difficult to use...we never set the temperature.

The device was supplied with an adapter.

Yes

The Philips HD9396/90 electric kettle does have a water level scale. This feature allows you to easily see the water level inside the kettle. As for the filter, the Philips HD9396/90 comes with a limescale filter, which helps to prevent limescale buildup and ensure cleaner water.