Why are Jing and Han Nuo kept in the pawn bottle at the end of No.8 pawnshop? What does this mean?

You mean the final outcome? If it's the end of the first film, two people are killed by fire, but Ah Jing is old and white. At the end of the third film, the souls of Ah Jing and Han Nuo are taken away by the shadow. Theoretically, they just haven't got rid of the fate of shadow control, just like their cruel parents. Hehe, this is my understanding.