Hi Nilton,
Let me help out here.
First of all, what you want to do is not supported out of the box.
Web interface reports will list web interface instances.
The WI instances are overwritten as process moves forward and new screens are launched.
BUT, there are some exception cases that WI instances will stay (so you can see old task screen).
1. At end of process - this is easily imaginable that, at end of process, WI instance will stop updating. This is true for Subprocesses too, you might be able to use this exception at your convenience.
2. At end of AND split branch - this is not so obvious and difficult to control, but WI instances always have "1" URL to access each. If AND split had 2+ manual tasks, there will be 2+ WI instances, and after AND join it goes back to 1 WI instances so there will be some WI instances that stop updating.
This is as far as I know, there might be other cases.
I think Subprocess method is easier to use.
You can consider making your current main workflow as a Subprocess of a "entry" process.
Entry process will have 1 activity, type Subprocess, and will launch the main workflow.
The WI should be set to launch the "entry" process, then it will generate a WI instance separate from approval tasks from the main workflow, and that one will never change.
Consider well and be careful about custom measures in above case, it might not work well since 1 WI will be attached to 1 process and 1 sub process.
Another way that is more straight forward is, to design your WI and process so that you don't edit ANY of the fields in launched form.
You can use Section widget, Tab widget, or other means to visually separate the submitted information, and in following screens NEVER let this part change. Only allow change in other areas of the page.
Best regards,
Taka