The first question:
Please download the latest version. It contains fix for the context menu control.
For the second question:
FlyTreeView maintains its nodes state. It maintains expanded/collapsed state, node text, node attributes/values, etc. Even if these settings were changed at client-side.
It also adds/deletes nodes at server-side nodes collection when you delete some nodes at client-side.
You can check it at
http://www.9rays.net/asp.net_2/treeview/Demo_ClientSidePopulation.aspx
Create treeview, arrange nodes in any way and click Postback. Then you'll see that all nodes are in their places. Server nodes completely reflect client-side ones.