Rare vs. Unique Item

1) Does anyone know what determines (when you use a magnifying glass) on a hidden potential item, what type of item will come out? Is there a chance for any hidden potential item to come out with a unique item (and thus have better % stats)?

2) Also, how are the 3 line potential items gotten?

3) Also, how are the skill items gotten?

4) Lastly, does the type of magnifying glass used influence how well the stats will turn out?

THanks!