Zorlac: ISPs charge a fee to host a dedicated, fixed IP address, vs. just getting whatever random IP address is assigned by their DHCP service.
dlarson54: it doesn't matter what kind of router you use. I can't think of a nicer way to say this, but the large majority of your questions have been so basic and obvious that perhaps you do not have the technical ability (or initiative to simply look things up yourself) to operate this equipment, and you should get your phone service from a bundled provider, and give up on DIY.