Hi Venkat,
The method IF_USMD_MODEL_EXT~READ_ENTITY_DATA_ALL should return the data of an Entity Type of type 1, and type-4 entities related to that entity type.
what are the parameters you are passing to the method? Check to see if you have any filter in parameter IT_ENTITY_FILTER.
I_FIELDNAME = Entity Type of type 1
IF_ACTIVE = Set the indicator if you want only Active version
I_CREQUEST = Change request number
IT_ENTITY_FILTER = Leave this Blank.
Hope it helps.
Regards
Kiran