Betty and Veronica are friends in the comic. Their friendship is depicted with various emotions and experiences, sometimes they get along great and other times they have misunderstandings, but it remains a friendship throughout.
Yes, there have been storylines where Betty and Veronica have shown romantic interest in each other or gone on dates, but it's not a constant or major plot point.
Definitely not. Such content is not suitable as it goes against the general standards of decency. Fanfiction should focus on positive aspects like character development, new storylines within the scope of the original's themes, rather than sexualizing characters.
Rivalry is another theme. Their competition for Archie's attention is a staple in a lot of Betty Veronica fanfic. But it's not always just about Archie; it can be about who is more popular or better at something in school.
It's a bit complicated. Sometimes Archie seemed to have stronger feelings for Betty, while at other times Veronica caught his eye. It really depends on the specific story arcs.