Hello Kayla welcome to our community
You are right with B. the Snowflake kitty is a costume kitty as we call them and their appearance is just to fancy up celebrations such as Halloween, Christmas etc. but are not possible to breed for.
So behind each costume kitty are the most dominant starter traits hidden in this case the Diamond fur and other Genesis traits.
They are similar to a normal starter kitty you can obtain in the KC main store.
Sometimes KittyCatS! includes special genes in their celebration kitties though which are specifically related to that special alone but I believe this is not the case with the Snowflake.
Last spring for example KittyCatS! brought the Wild Flower Kitties and the Scrambled eggs collections via these kitties there was the possibility to breed a random crystal eye not available via their regular starters.
These things they mention in their release notecard.
Basically it is a Genesis Diamond with a fancy costume :-)
What the kitty is hiding behind those starter traits can be found out via breeding them with for example a recessive and high traited kitty and when you receive a box with a fair amount of non starter traits there are basically two approaches.
Some people like to back breed them and others like to breed two siblings which show other than starter traits and pair these up.
Back breeding can give you faster results so that is the benefit of back breeding.
The benefit of sibling breeding (my favorite way) is that you know the kitties hide all the traits your starters partner had in case of a 9 traiter kitty the chances are higher the siblings will give you a better traited kitty.
I hope this helped to clarify this a bit.
Good luck!
Kay