Can we track who has edited or updated replica layer (versioned) of sde feature class at different times. I would like to find out how many people have updated a versioned feature class say from last six months or so. I am using Arc Map 10.1
You would need to have enabled Editor Tracking on the data prior to it being collected in the field. Here's a link to some resources:
Enabling and managing editor tracking—Help | ArcGIS for Desktop
About tracking an editor's changes to data—Help | ArcGIS for Desktop
Enabling editor tracking on multiple datasets—Help | ArcGIS for Desktop