To get the workflow context you need to retrieve the workflow via 'WorkflowUserTask_Workflow' and then use the 'Retrieve Workflow Context' actions to get the context. (There's also a more generic Java API).
You will still need to find the correct page then for display.
We've struggled with similar problems. Overall this part of the Workflow Engine is not flexible enough in my opinion.
As a workaround you could use a microflow timer on the target page, that redirects the user to the correct device page.