When multiple change requests that affect the same control account/work package are submitted concurrently and a change request is applied, only the data you changed updates the live project. This means that there is never a problem with the data in the sandbox being outdated.
You have an activity with a duration of 5 days. Three change requests are submitted simultaneously. They are approved in the following order:
Change #1 updates the activity duration to 13 days.
Change #2 updates the activity resource assignments.
Change #3 updates the activity duration to 9 days.
When each change is completed, only the data that has changed is applied to the live project. Since the "last approval wins," and change #3 was approved last, the final activity duration is 9 days.
The benefit of this process is that progress, and so on, that is entered while the change is getting approved, is retained when completing the change request.
Create a Budget Change Request
Create a Forecast Change Request
Create a Contract Change Request