I will.

Yes, I think what we have created two instances on node 1, one is for pro, th other is for qa, then we added the same two instances on node 2.

Does that mean when install the second node, He only added the node, he didn't install the two instances again with same names on node 2.

Also when applying service pack, do I need to run on both nodes even the passive one ?

This is a SQL server 2008 cluster.

Thanks