"Wild at Heart" - the amount of "available" slots is ten (10); any spare cards beyond this amount act like normal cards (eligible for gold drop and so on). [on a related note, you can ony hold nine (9) of any given piece of gear in your inventory at once, including equipped slots]

"Unleashed" refers to active ability cards.

Beating the game on difficulties higher than "Relaxed" will unlock the corresponding lower achievements so you don't have to beat it three (3) times.