Adult Womens Retro Go Go Girl Fancy Dress Costume

Need this by Saturday will it arrive in time if i order tomorrow?

I have purchased this item & I am normally a size 8, but I didn't have an option to change the size, what would I do?

I’m a 16 - should I go for the 14-16 or 18/20 - what’s the sizing like?

Does the dress get longer as you go up a size? From small to medium?