Execute dynamic query using SP_EXECUTESQL returns Null in SQL Server

i have the Following sql code:

print @c_query----- output: SELECT METER_REGISTRATION_ID AS ID,METER_REGISTRATION_ID AS NAME FROM [dbo].[D0150_NHH_METER_TECH_DET_T] WHERE REG_ID=
SET @TEMP_ITEM_VALUE = N'SELECT TOP 1 ID FROM (' + @c_query + '' + Convert(Varchar(max),@REGID) + ') AS ID'
		
print @TEMP_ITEM_VALUE---- output: SELECT TOP 1 ID FROM (SELECT METER_REGISTRATION_ID AS ID,METER_REGISTRATION_ID AS NAME FROM [dbo].[D0150_NHH_METER_TECH_DET_T] WHERE REG_ID=9217) AS ID
EXEC SP_EXECUTESQL @TEMP_ITEM_VALUE, N'@RESULT NVARCHAR(200) OUT', @RESULT OUT
print @RESULT----- Expected Result: s but getting null
		
IF(@RESULT IS NULL)
BEGIN
    print 'null'
    SET @ITEM_VALUE = ''
    END
ELSE
BEGIN
    SET @ITEM_VALUE = @RESULT
END

what i am doing wrong here? i am getting null.

Is my format is right?