Ultiboard 11.0.2 - when selecting parts in a window or individually, parts on both sides of the board can be selected and moved. This is true even though only one side of the board is visible. Is there a command that toggles that feature, or is there a default selection box size that's too large? I haven't noticed this happening before. I'm working on a very dense board, and can't be accidentally moving parts on the non-visible side.
Just to clarify, you want to work with an individual part in a specific layer without modifying any other overlapping part from other layers, correct? You mentioned that even though you dont have those other layers showing, you still select the parts in them that overlap with your own. I'm assuming this has to do with the fact that you have only hidden the other layers, not disabled them. In your left design toolbox section, double click on the layer you want to work with and then click on the boxes next to the layers you want to avoid until the boxes are white and empty. This way, you disable them and can comfortably work on the one active layer. You can always reenable them after you're done working on one part. Let me know if this helped.