Hi Praveen,
You can use BTDocflow entity to find parent of any document. You need to navigate to BTDocflow from BTAdmingH using get related entities and get the parent object guid in field OBJKEY_A refers to the parent document guid and OBJKEY_B refers to the current document guid.
Once you get the paretn guid for one level then use crm_order_read function module to read parent document docflow details and from then take again objkey_a value which will be parent of that document and then go ahead with next orde read fm to get again parent of your document. You have take objkey_a value every time until you get the required document guid.
Best Regards,
Dharmakasi.