Ok, let me see if I can walk through a couple of things to see if it clears up some mysteries.
I tried the steps you describe to set a background picture for slides and don't see any effect unless there is no background to start with. That is if I start with a slide with no background and put in a picture that becomes the background. If however I already have a background then following the right click slide>set background> does not produce any change.
Right. It's a little confusing, but the file you uploaded seems ok in this.
The confusing thing is that there are two different ways to set a background, and they can interfere with each other.
Right-click > Slide > Set Background Picture for Slide (or Format > Page > Background > Fill = Bitmap) fills the area of the slide rectangle with a bitmap pattern, similar to filling it with a color. In the case of an image, the bitmap pattern is large and does not repeat the way the other bitmaps do. That fill is the farthest "back" that you can get: everything else on the slide will overlay it.
The file you uploaded uses the Insert > Picture > From File method. This method simply has a normal picture, sent to the back, but that is still over the background fill. So when you tried Right-click > Slide > Set Background..., the area fill is still underneath and obscured by the image object and it appears to have no effect.
If you go to the master view, click on the slide background to select the picture, then press "Delete", you remove the background image object. The other slides use the master, so the background disappears from all the slides as well. Now, if you use Right-click > Slide > Set Background..., the change will not be obscured and you can see it take effect.
Neither is more "correct"--you can use whichever method you want.
... if I go to a notes view I do not get the slide in the top part of the window.
Right; I see that too. The slide in the notes view appears for some slides but not for others. However, the slide appears if I click on the layout sample in the panel on the right. I've not seen that before; my guess is that it's just a bug.
If I select all the slides (use the slide panel on the left) and then click on the layout sample, then all the slides appear in the notes view.
I had put some in when I made some of the slides but they are now gone.
I see notes on many of the slides--are you using the "Notes" view (tab at the top of the center panel)?