You must use the same multi cast address and partition name if you want to have a cluster of the nodes.
The bind address must be different (on the same machine) or you have to use port-binding.
1+2)
If nodes join a cluster you will see messages like 'New members' + 'All members' on all nodes (If you start only one this node show the message '# of members : 1' and its own data
You could check via JMX console, look for the server-cluster beans, you will find the same information like you see in the message.
3)
see wiki for a simple test https://community.jboss.org/wiki/TestingJBoss