1. You need to Bake the Normals of the high resolution model, and apply the normal map result to the low poly object.  The baked normal map will change the appearance of the low poly model, to approximate the smoothing and details of the high poly version at a distance.

2. You can see the statistics of any selected object at the top of the screen, next to the render engine drop down box.  In object mode, you will get the overall statistics, and in edit mode, you get the stats of the selected object.  There are other ways to retrieve this information as well, but that's the basic, fast way to ascertain certain details.

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