As I understand it, your requirement is to have a flow with an assignment where users have to enter some information. After they enter the information you would want to update few more properties on this WO and based on some flag you would want to resolve the work item. Is my understanding correct? If so, you can define a post processing activity in the flow action and queue the WO for the agent. In the activity for the agent, you can open the particular WO and set the properties you wish and based on the check you have you can resolve the work item.
We should not open the WO. We have created the WO by some activity and WO id is saved in external DB table. that work object is having a single assignment. Now I need to write an Agent activity to query the DB table to get the WO id . then I need to open the WO and set some properties on that page after that I need to finish the Current assignment from Agent activity only.