While these are all valid questions, this has been covered by releases from the FCC. See my post FCC Imposing New 9-1-1 Rules for Multi-Line Systems it has the links for the docs the FCC sent me on this.
I’m going to be honest here, if you are a company that will be hit by this because you install PBX or offer voice services then you need to deal with this through proper channels. Trying to make sure you’re in compliance by asking questions in an OSS project forum isn’t the best practice for something like this.