If it is an older switch/combi, it might be worth replacing it. Newer models are sometimes less deep and there is room for the shelly in the box. It is best to measure the depth and compare it with the T-measurement of new switches/station wagons.

Yes I think so, but I am not an electrician ;)

https://www.shelly-support.eu/forum/index.php?thread/84-shellys-gehen-offline/

Yes, you are wrong. This Shelly can only switch on/off. This one should fulfil your purposes: Shelly WLAN switch actuator 2.5 To be on the safe side, I would briefly go through the operating instructions: [https://shelly.cloud/knowledge-base/devices/shelly-25/#wiring https://shelly.cloud/documents/user_guide/shelly_25.pdf Unfortunately, I have not yet been able to test this type, as I do not have any electric blinds.

Yes, it is perfectly zigbee compatible, I use it with Home Assistant without any problem.

No, no controller is necessary. When initially put into operation, they are an access point. Connect to it and then configure it in the browser. They also only understand 2.4 ghz. It is well documented. Google is the best source of help here.