I never wrote Minho forgiving Dahlia or how Finn was doing or anything so uhm here are the replies

"Who is Hazel?"

Hazel is Thomas & Viviette's daughter. She was born when they were twenty-six and was six in the epilogue. 

"What are their jobs?"

Thomas does something close to Dan (math things I don't understand) and Viviette has her own clothing brand.

"Did Minho forgive Dahlia?"

Imagine he did forgive her, but their relationship never remained the same; always a tad awkward and tense.

"How are Finn and Sylvia doing?"

Still fine— probably also married.

I apologize dearly that I did not make this clear in the epilogue and have to do it sloppily like this. Still hope you enjoyed!