Answering your questions it will
1) work with the coax outlet of your SAT-Dish connecting it to the first (A) input of the Netstream 4Sat. You will be able to receive one SAT channel and send it to 1 device
2) work in the mentioned way with an AppleTV if it is a ATV4 version and has the Netstream app installed.
You will NOT see any encrypted channel (SKY, HD+, ...) as the Netstream does not have a CI-Slot for smartcards. There is a workaround running an OSCAM server solution in your network, but there is no OSCAM client for the AppleTV.
So if you want to see encrypted channels you better go for a Dreambox or VU+ receiver and an app like vuplusTV on the AppleTV.