Use layers to put one object above or below other objects, once made. Using the Layer Palette, you can drag one layer/sub-layer into either position in relationship to others.
Select an object, CONTROL C to copy it, then either Control V to paste it to center of artboard, or Control F to paste directly over and in front of the original.
You can also do a drag n drop duplication of an original by selecting the original, then as you start to drag the object, hold down ALT key and release the ALT key when you wish to drop it. Do this as many times as you'd like or need to.
Bob
The container should be a rectangle, circle, free-hand shape etc, drawn Illustrator. You can mask Illustrator-drawn graphics or imported photos etc.
Once the mask is made, you can adjust/scale the position of the masked object using the Direct Selection Tool (white arrow).
I've been looking for some of your answers to see if I can follow your style of writing --"stream of conscousness". You type as if you are thinking to yourself at a keyboard. Because this is instruction that you are offering up to the public, I suggest you also use "--" and "..." and "....", so that the reader can figure out when you pause, when you make an aside, and when you are finished.