Once we submitted change sets to OSM server how we can monitor user history about their past change sets?
All concerning QA is answered here:
http://wiki.openstreetmap.org/wiki/Quality_assurance
For example:
If you want to have a look at user history, you can see your own for example at http://www.openstreetmap.org/user/MalingaGIS/history
For a specific area have a look at Whodidit, e.g. http://simon04.dev.openstreetmap.org/whodidit/
More reports are available at: http://resultmaps.neis-one.org/