有關relative clause?

1) Hong Kong, which we live in, is prosperous. 正確。
2) Hong Kong, in which we live in, is prosperous. 錯誤，應刪去第二個in。
3) Hong Kong, where we live in, is prosperous. 錯誤，應刪去介系詞in，因為where是關係副詞，不能當介系詞in的受詞。

Second question:
一般是 whose + noun + V + O
e.g. I met Mary, whose brother is my friend, last week. 正確。
但 whose + noun + S + V 也可以?
The girl stands here, whose name I don't know, is beautiful.錯誤。因為主句的述部是stands...，沒有使用對等連接詞，不能再出現另一個述部is ...；此外，形容詞子句whose name ...不宜與其修飾的名詞girl隔開。
whose name I don't know裡whose name是子句裡的受詞，這個relative clause的結構，在文法上是正確的。

First question:
main clause: Hong Kong is prosperous.
relative clause: We live in Hong Kong.
合體後,以下那款較好?
1) Hong Kong, which we live in, is prosperous.(差)
2) Hong Kong, in which we live in, is prosperous. (錯)
3) Hong Kong, where we live in, is prosperous. (錯)
4) Hongkong, where we call it home, is prosperous.
5) Hongkong, our hometown, is prosperous.

Second question:
一般是 whose + noun + V + O
e.g. I met Mary, whose brother is my friend, last week.
但 whose + noun + S + V 也可以?
The girl stands here, whose name I don't know, is beautiful.

My answer to your second question:

Stop memorizing formulas and equations in learning languages.
Start reading a good book and enjoy the language.