I need to work on "Checked Out" version of a geodatabase, editing geometric networks. What will be the difference in terms of the working process of the editor ?-do i need to use some special toolbars ? is it possible to work on versioned GDB with ArcEditor 10.1 ?
I don't understand exactly what you're asking.
Read this to learn about the different replication types:
A checkout will either be a personal or file geodatabase. It should look and feel the same as editing from an SDE database. It's just a copy of the SDE data that can be worked on in a disconnected environment and then is checked back into the SDE database when you're finished editing. Any edits you make will be applied to the server once your data is checked in.
And, yes, it is possible to work on a versioned geodatabase with 10.1.
You don't need to worry about this. Working with the checked out geodatabase is not different than working with a non versionned data: all the work is on the side of the default version.
What you need to care about is to make sure that you don't have a conflict between your ArcGIS release and the one where the data comes from (see here). If you version is higher, do not upgrade the gdb!