Straight onto your questions:
a) You can add records using RadGridView in exactly the same way as in MS DataGrid. You need however to execute SubmitChanges() for both grids to publish new data to the server.
b) Indeed validation is now supported - please check this post
for more info.
c) There will be no problem to use masked edit in your cell template - please check this demo
d) We don't have anything extra (automatic) or unusual here - same as MS DataGrid.
the Telerik team