Potential System, halp

1/ So the randomness at applying a potential scroll to the item is the chance at acquiring its rare, unique, epic, etc statuses, right?
2/ What are the differences among the aboves? I heard that an item can have up to 3 stat-bonuses with up to 21 units per stat-slot; stackable.

I think I got the rest, thanks for your answer.

It also depends on the level of the item:

This is in terms: (rare, epic, unique) ... these are the possible stat+%
under 50: 1/2/3
51~can't remember:2/4/6
cant remember~120: 3/6/9
120+: 4/8/12


So a rare lvl 30 item could possibly get +1% to a stat, but a rare lvl 100 item could get +3% to a stat.


On the other hand, unique items near lvl 120 (but not over) could get a +9% to one of their stats