Added to my list for the „worst questions pageant“. Please see How should I ask a question in the Forum if I want to receive useful answers? And try to provide any useful information what does not properly work so we don’t need to be thelepathic.

I concur with Ralph on this one. It appears that what you try to do is very messy and you don't even have clear understanding how relationship between work items works.

I'm very curious how you managed to "create query to display defects which having literals selected as 'A'". That is simply impossible - for one, the Defect work item does not have the said Enumeration attribute, and because of the Work Item List attribute in Defect is multi-valued, you cannot access the Enumeration attribute in the linked Task work items in a query either.

Why do you have four Work Item List attributes in Defect? The custom attribute name does not magically map to an Enumeration with the same value.

If you can explain why you design Defect and Task the way you have done, we may have better understanding of what you want to achieve.