A:AnswerYou don’t have to be in the same room though I have not tested the range. If your watch has its own plan then no not at all it can function separately
A:AnswerI also had difficulty initially. I reread the directions and saw that the watch needed to be charged for 18 hrs. Once I did that things worked, at least on my watch.
A:AnswerI don't have the cellular option on my phone, but as long as it is in proximity of my iPhone, it shows incoming calls and text messages without my having to take my phone out of my pocket. Very convenient.