No, it won't work, you need an analogue telephone on the output of the Salt box or check with the operator as you certainly have a residential subscription.

You can enter your SIP trunk directly into the Yealink SIP-T54W phone without the need for a 3cx or FRITZBox. The phone supports up to 16 VoIP accounts and enables the direct configuration of SIP trunks via the device's user interface.

This is called sustainability in order to avoid electronic waste. Today, very few devices are still supplied with a power supply unit, especially since most networks supply PoE (Power-over-Ethernet) and no power supply unit is needed.

In the web interface there should be an option "remote phonebook", under this tab the API can be entered and configured. Please check if the firmware of your phone is up to date. Otherwise, I recommend contacting Yeallink support: https://www.yealink.com/contact.html

Our supplier is unfortunately unable to answer. But checking online, we found that v2 simply has the updated chipset, there is no difference in functionality.

If you are using a PoE injector, you must make sure that the cables are connected correctly. In principle, you can plug a patch cable into the "Internet" socket. It is also possible to establish a WLAN connection via menu navigation on the telephone. Then you must configure the line via the web user interface (IP address can be seen in the menu --> Status) via IP address. Here is a manual for Fritzbox and Yealink. Not the same phone but similar views: https://www.hilasys.com/2018/07/07/konfiguration-yealink-t21p-e2-voip-telefon-an-fritzbox-7490/

It is best to contact the customer service department at https://helpcenter.galaxus.ch/hc/de/requests/new directly. Your request can then be examined individually.

None. Bluetooth is integrated.