Hi Stephanie,
The Demo doesn’t work any other way than the full version. The box can randomly appear on 2 sides of the model - I guess it was on the bottom when you first tried it. Once you get the hang of removing it, it doesn’t take too long. Especially with a person on a flat surface with no interference of any geometry from the sides, it should be pretty straightforward.
The component breakup can be caused by many different reasons, hard to tell wothout any further info. It is true that it sometimes happens that other software aligns more that RC, but ultimately RC provides MUCH higher detail. Like all other software, it has a learning curve, unfortunately a rather steep one (I find) after the initial Oooh.