cluster_database TRUE/FALSE what does it mean in Oracle RAC?
What the SIDs on all the nodes? Is this really the same DATABASE. For example you can have 3 node cluster having a single ASM on all the nodes, but database A is clustered on node1/node2. But database B runs only on the node 3.

The database B then is still started and stopped by the Clusterware, but is not clustered. You can also check output from:

ps -ef | grep -e lmd


The lmd process is started on clustered instances only.

EDITED: maybe I understand now. You do not have RAC database. RAC is active-active cluster. .i.e databases instances run on multiple nodes at the same time.

You have standalone instances guarded by Oracle Clusterware. So you have active-passive failover cluster. As described here :Using Oracle Clusterware to Protect
A Single Instance. Then you do NOT need the parameter cluster_database set to true. It only applies to RAC databases.