ItzMeteor_WolfPlayz

I found an article that might explain your answers ( Kinda long)
https://zhuanlan.zhihu.com/p/166207012

The author likes to sell books to different companies that's why

Tomb of the Sea is actually years after that, and there is some more books before it ( waiting for it to be filmed). I'm pretty sure tomb of the sea is around 10 years after this book ( won't spoil or go into detail :) ), and the reunion series is putted after the tomb of the sea.

Well the problem is, like all the other series, the author sells each book to different people to make the series. ( The author never sells the whole series to one company and he leaves a lot of questions and cliffhangers in the book, and this director of the TV series did a pretty good job on trying to fix it.) The book probably ended like how it ended in the tv series ( they did have a short clip after but still a cliffhanger.) ( Btw, fun fact, Zhang Qi Ling/Xiao Ge was a girl originally I think, but then the author (I think) figured that "girls" like these "BL" type of books more, and it is a faster way to earn money. )

if you're talking about the one that was "bathing" by the water and got bitten then it is A Ning.