Depends very much on the environment and sources of interference. 40m may or may not work. At best, something with directional characteristics would be more stable.

It depends very much on the environment. We use it in the underground car park to amplify the WLAN there up to the hobby rooms, i.e. it amplifies the WLAN through one wall or another. In this scenario it works very well, without major obstacles and with both network modes 2.4 and 5GHz it should manage the 40 metres.

no idea! I dipped it for the cellar! it went very well!