HavaianasWomen's Slim Crystal Flip Flops

Is a size 9-10 the same as 41-42 in haviana slim flip flop?

I wear a size 6 1/2 shoe. what size should i get in the havaianas womens slim crystal 2 sandal?

Do these actually have the crystal on them??? I've ordered 3 times and nada! Pic/Description states crystal, which is the cutest part!

I wear a 8 1/2 shoe, What sizw should i get the havaianas sandal in?