Sql query check instance name and sever name

SELECT @@servicename AS Servicename --returns instance name, even if this is the default (MSSQLSERVER)

SELECT SERVERPROPERTY ('InstanceName') AS InstanceName --null mean is defalut

select @@SERVERNAME AS SQLclusterName

SELECT   CONVERT(char(20), SERVERPROPERTY('servername'))AS WindowsClusterName --use this name to connect to db

SELECT @@SERVERNAME  AS pre_change_name, --returns servername\instance as far as this is not the default instance

 Serverproperty('Servername') AS current_server_name