You can execute below script to get Symantec NETBACKUP version and patch information.

set nocount on

CREATE TABLE #OUTPUT(
	[SQLInstanceName] [nvarchar](128) NULL,
	[WindowsServerName] [varchar](30) NULL,
	[NetBackupClientVersion] [varchar](255) NULL,
	[NetBackupPatchVersion] [varchar](255) NULL,
	[NetbackupStatusCheck] [varchar](28) NULL
) 

declare @regkeyval varchar(20), @value varchar(255), @rc int
exec @rc=master.dbo.xp_regread 
  @rootkey= 'HKEY_LOCAL_MACHINE',
  @key='SOFTWARE\Veritas\NetBackup\CurrentVersion\',
  @value_name='VERSION',
  @regkeyval=@value output

set @value =isnull(@value,'-')

declare @Pvalue varchar(255)
exec @rc=master.dbo.xp_regread 
  @rootkey= 'HKEY_LOCAL_MACHINE',
  @key='SOFTWARE\Veritas\Patches\NetBackup\',
  @value_name='PatchLevel',
  @regkeyval=@Pvalue output

set @Pvalue =isnull(@Pvalue,'-')

if @value <> '-'
insert into #OUTPUT(SQLInstanceName,WindowsServerName,NetBackupClientVersion,NetBackupPatchVersion,NetbackupStatusCheck)
select 
 @@servername as SQLInstanceName
,case serverproperty('IsClustered') when 1 then cast(serverproperty('computernamephysicalnetbios') as varchar)
 else cast(serverproperty('machinename') as varchar)
 end as WindowsServerName
,@value as NetBackupClientVersion 
,@Pvalue as NetBackupPatchVersion
,'NetBkup is installed' as NetbackupStatusCheck 
else
insert into #OUTPUT(SQLInstanceName,WindowsServerName,NetbackupStatusCheck,NetBackupClientVersion,NetBackupPatchVersion)
select 
 @@servername as SQLInstanceName
,case serverproperty('IsClustered') when 1 then cast(serverproperty('computernamephysicalnetbios') as varchar)
 else cast(serverproperty('machinename') as varchar)
 end as WindowsServerName
,'NetBkup nt installed' as NetbackupStatusCheck
,'0' as NetBackupClientVersion
,'0' as NetBackupPatchVersion 

select * from #OUTPUT