What's the status of LED on NC450? Except playback, do other function work properly? You can check whether the FW is the latest one. If it' s not, it' s better to update firstly.

Generally speaking, it should support that. You can get a hub to test it easily.

Is the wifi extender powerline device plugged in the gardenhouse? How far between them? or you may try to change the wireless channel on the wifi extender.

It states 100-120v becasue the US standard is 100-120v. But it still can work under 240v.

Can you control plug via kasa app remotely? Firstly,make sure kasa remote control is working well. If remote control from kasa is working properly, you may try to remove device on google home app and...

after you changed the password, can you still control the bulbs normally from kasa app no matter locally or remotely? Make sure the remote control via kasa is working firstly. Then, forget the kasa...