Hi, Unisclosed #2, Thank you for your comment.
I will try to answer your questions:
To select a box or wall you can click on it, or press a mouse button and draw a frame around objects to select. Sometimes it is tricky to select a door that is inserted into a wall. In this case please double click the door or click it multiple times till it is selected.
Undo function is CTRL+Z (Redo is CTRL+Y) as in MS Word. Also in version 9.1 we added orange Undo/Redo buttons in the main toolbar.
To prevent an accidental moving of some objects or layers you can lock a layer (using Layers button in the toolbar and then press lock icon) or lock some objects by Lock In Place command in a popup menu for the object (do right-click the object to open the popup menu).
Please don't hesitate to contact us via support@jvsg.com.