How much info share bitcoin nodes between other nodes?
The IP-addesses of Bitcoin nodes are not a secret. See addr
Nodes don't explicitly tell other nodes their Bitcoin addresses. Since nodes pass on details of other nodes transactions, working out which nodes originated a transaction isn't straightforward.
Since the set of Bitcoin nodes is constantly changing, and nodes go offline temporarily (or permanently), no node ever absolutely and definitely knows the IP-addresses of all nodes existing
Nodes don't communicate with all other nodes. Only with a few at any time.