Regarding the questions:
1) The expand/collapse doe not work with virtualization. This would be possible only if there was a requirement of all data to be available to the grid which can lead to performance issue if millions of records have to be requested at once.
2) With the virtualization, the last item begins in the top of the last page, not at the bottom.
3) Not sure I understand your last question, some further details on how to replicate would be in help.
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items