iCloud. You need to be logged into iCloud.
Phone calls: Your service provider must have this service as well. I think they all do now, Verizon being the late comer.
On the iPhone under cellular, enable calls on other devices. A code will pop upon the iPhone and you enter that code on your laptop or iPad. Enter code and you are good to go. . I can make calls on wifi with my new iPhone ++++++++++++ (iPad Air) even with my iphone shut off, the same with my iMac.
Messages: In Messages make sure you have your iPhone’s number entered as one of the Messages ID’s and it is checked.