Real-world cross-platform decentralized asynchronous peer-to-peer communication

Question

My knowledge about network programming is limited, so, all the comments are more than welcome. Essentially my question boils down to the following question:

Q1. Is

Answer 1

You asked many questions, here is the beginning of the answers:

Q1: Yes. For example, take BitTorrent's very successful 10 million+ node network. Aside from the bootstrapping process, the protocol is entirely decentralized and asynchronous. See here for more info.

Q2: Yes! Go to www.whatismyip.com on your mobile telephone, and you will see your assigned IP. However, you are likely to be very filtered (e.g: incoming traffic on port 80 is likely to be blocked).

Q3: It has elements of P2P and clever tricks to get around NAT issues - see here for more info.

Q4: I don't know.