Yes, Dark Betty did exist. She was often a departure from the typical portrayal of Betty, bringing a darker and more mysterious element to the comic series. Her appearance and character traits were designed to surprise and intrigue readers.
No, Betty isn't insane. She's often shown as a kind, friendly, and sensible person in the comic series. Her actions and behaviors are typical of a normal character.
It's a bit complicated. Sometimes Archie and Betty have romantic moments, but their relationship status often fluctuates. Different comic arcs present different scenarios for them.
Archie does date Betty in the comics, but it's not a consistent or exclusive relationship. There are many storylines where his affections shift between different characters.