Finally I was able to fix my code...My Mistakes were need to read the parent node above three levels and need to use the relation entity name while reading the data..
Below is the correction code
IF iv_index IS NOT INITIAL.
lr_iterator ?= collection_wrapper->get_iterator( ).
lr_current ?= lr_iterator->get_by_index( iv_index ).
lr_entity ?= lr_iterator->get_by_index( iv_index ).
ELSE.
lr_current = collection_wrapper->get_current( ).
ENDIF.
*loop back to root entity
WHILE lr_entity->get_name( ) NE 'BTAdminH'.
lr_entity = lr_entity->get_parent( ).
ENDWHILE.
*Get the related entity
IF lr_entity IS BOUND.
lr_collection ?= lr_entity->get_related_entities( iv_relation_name = 'BTHeaderOrgmanSet' ) .
IF lr_collection IS BOUND.
lr_orgset_m = lr_collection->get_current( ).
* lr_orgset = lr_orgset_m->get_related_entity( iv_relation_name = 'BTOrgSet' ).
lr_orgset = lr_orgset_m->get_property_as_string( 'SALES_ORG' ).
ENDIF.
ENDIF.
Thanks,
Sapsar.