Chased SME's, analysis and commuinication... Below is the final list of queries still pending from your side:
1. Discount Amount query asked in the previous mail.

Waiting for stakeholders feedback...

2. The default value mentioned by you in the Reference Type field in the POLL 4 file is document number. So should this be the order number or anything else? Can you please let us know the exact value expected here?

I made a mistake on this, Reference Type should be null. I believe your question was really for Misc Reference/Info. 

Where...If COD = Null , If PayDollar = Should contain Document Number. Document number = generated transaction reference from the payment channel. Normally generated and return with the approval code (Credit Authorisation Code). 

If data is not available, random sixteen digit numeric value will suffice. 

Thank you for catching this for us.

3. If the order doesn't have any discount codes available what should the default value pass in the Subtotal Discount Amount, Item Discount Reason Code and Transaction Discount Reason Code as all this 3 are mandatory fields? 

If no discount is applied, Subtotal Discount Amount, Item Discount Reason Code and Transaction Discount Reason Code can be assigned with null value. 

Validated with our JDA team and realised that the three columns should have a Mandatory value = NO on the reference worksheet. 

Thank you for catching this for us as well.

4. Regarding the field TNFCCD(i.e. Credit Card Number) Shopify doesn't provide the entire credit card number, only last 4 digits are available in the API response. So is it ok on your side? Please refer this API for reference https://help.shopify.com/en/api/reference/orders/transaction#index

Yes, last 4 digits is fine. 

5. Regarding the Credit Card Expiry Date field, the API doesn't return the same as per the reference mentioned in point 4, what should be the default value in this case?

Assign it with a Null value.

6. What i