BL manhwa refers to Boys' Love comics or graphic novels that come from South Korea and feature romantic or intimate relationships between male characters.
Hard to say for sure. It might introduce a new character or deepen the relationship between existing ones. Or perhaps there's a big decision that has to be made that affects the course of the story.
Well, a rut bl manhwa usually features male-male romantic relationships and explores various themes related to love and emotions. It's a popular genre in the world of manga.
To survive as a villain in a BL manhwa, you have to be strategic. Understand the weaknesses of the heroes and exploit them. Also, build alliances when it suits you, but be ready to betray them if necessary.