The link is here: http://www.tp-link.com/us/download/TL-WPS510U_V6.html#Utility , but it is for windows only. You need to click the corresponding hardware version and click utility to get it. For MAC...

As I know, there is no client-only mode on the TL-WR841N. With WDS enabled anf Wi-Fi function disabled, the 841N may act like a client though.

There is no notification on the kasa as far as I know. It will show on kasa the Power button is green, but no notification would pop up.

I guess you still need someone to help you get it back first. And later you may check the firmware version and the signal strength on the smart plug. You can get both of them under Device settings in...

No, at present Alexa cannot schedule the HS100, only kasa can

have you enable remote control on the kasa App for the plug? And do you have a TP-link cloud account? you can refer to this http://www.tp-link.com/en/faq-944.html