Yes, it's very likely that Alexandra is a character in a Harry Potter fanfiction named 'Alexandra Quick'. In many fanfictions, the title often features a main character's name.
As I said before, without more context, it's hard to determine who they specifically are. They could be just ordinary people in a small town with their own simple and beautiful love story, or they could be figures from a certain historical era or a fictional story.
Yes, in the 'It' novel, Richie was gay. Stephen King included this aspect of his character which added depth to Richie's personality and his experiences in the story.
Richie wasn't gay in the novel 'It'. The author didn't present his character in that way. The plot centered around other elements rather than Richie's sexuality.
Whether Richie is gay in the novel isn't always straightforward. It could be left ambiguous for the reader to interpret or could be revealed gradually as the story progresses.