three differences between a real object and a virtual object as they arise when one is using a diverging lens?

Answer 1

1st answer is correct as far as it goes. I think you're asking about all the differences between real and virtual images. When using a diverging lens you see a virtual image through the lens; it's upright and smaller than the object. With a converging lens, a real image is seen as a projection on the opposite side of the lens from the object, provided the object's distance L1 from the lens is greater than the lens's focal distance F. The image is inverted and can be larger or smaller than the object. If L1 > 2*F it's smaller and its diistance L2 from the lens is less than 2*F; if L1 = 2*F, it's the same size and L2 = 2*F, and if F < L1 < 2*F it's larger and L2 > 2*F. There's a good explanation in the ref.

Answer 2

You mean to say real image and virtual image. The object is real always, except in case you are using more than one lens.

The real image can be seen on a screen. The virtual image can not.