To check the current node/Active Node where the SQL Instance is running, you can execute the below query.
select serverproperty(‘ComputerNamePhysicalNetBIOS’)
To find out all the nodes of the SQL Cluster, you can use the below DMV.
select * from sys.dm_os_cluster_nodes
To find out if the instance is clustered, you can use below query, if it returns 1, then the instance is clustered
select ‘IsClustered’, serverproperty(‘IsClustered’)