I'm installing a couple of Nest Hellos for a client. The FAQs that I see neatly answer just about everything except for these questions:

*I'm installing it. Do I have to get the client's phone and use it for setup for him to be able to use its functions?

*Is it a problem to use one power transformer to run two Hellos?

That ties into the other question:
*The instructions say the Hello is meant to be installed where there's already a chime. They go on to say that's because the transformer powers the Hello. (This client's house has neither chime nor transformer, but I just bought a chime transformer to power the unit.) Is it necessary to also get an actual chime to be part of the circuitry? Or might some load resistor be needed?

Thanks for any help.