How to identify multi instance subprocess and differentiate it with main process in BMP?

Issue

• I have used one multi instance subprocess which includes an workflow with human task. When executing, its creating the number of human tasks as to the number of elements present inside the collection object. But all task have same process instance id. How the relation is working between parent process and multi instance subprocess?

• If ther are multiple elements in collection list, then it will create those many tasks inside the multi instance sub process. As all the tasks have same process instance id, how to identify the respective process variable values for each task and the uniqueness of each flow afterwards.