Linked Server returns only one row while reading remote server registry

The below script is to read registry information using linked server, however it returns only one row instead of multiple rows.

SELECT a.* FROM OPENQUERY(LinkedServerName,
  'SET FMTONLY OFF; Exec ('' Use [master]; 
  DECLARE @RootKey VARCHAR(30), @InstanceName VARCHAR(100), @Key VARCHAR(200)
  DECLARE @StartupParams VARCHAR(100), @InstanceVersion VARCHAR(50), @InstanceValue VARCHAR(200)
       SELECT @InstanceVersion = @@serviceName
  --SELECT @InstanceVersion
  EXEC master.dbo.xp_instance_regread ''''HKEY_LOCAL_MACHINE'''',
  ''''SOFTWARE\MICROSOFT\\Microsoft SQL Server\\Instance Names\\SQL'''', @InstanceVersion, @InstanceValue OUTPUT
  SELECT @InstanceName = @InstanceValue
  --SELECT @InstanceName
  SET @RootKey = ''''HKEY_LOCAL_MACHINE''''
  SET @Key = ''''SOFTWARE\Microsoft\\Microsoft SQL Server\'''' + @InstanceName + ''''\MSSQLServer\Parameters''''
  exec master..xp_regenumvalues @RootKey, @Key
  '')') a