In which x which...in: Como utilizar

1. Choose in which room you want to stay.

2. Choose which room you want to stay in.

1-As duas estão corretas?
2-Tem alguma diferença de sentido entre elas?
3-Eu posso usar sempre com qualquer verbo e situação?
4- Esse artifício de separar tem Nome?

Eu sei que são muitas perguntas, mas se puderem me responder irão me ajudar muito

1. Ambas.
2. Nenhuma.
3. Depende do contexto.
4. Preposition at the end.

Frase 1 = Num contexto formal.
Frase 2 = Num contexto menos formal ou, simplesmente, informal.

A: "Which street did Zé say he waited 19 hours and a half for Maria on?"¹
B: "Lambaster Street 123. In front of the movie theater."
A: "Oh my God! Did she show up?"
B: "Yes. On the next day. I guess they missed the movie they had planned to see."

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¹ On which street did Zé say he waited 19 hours and a half for Maria?

Marcio_Farias escreveu:1. Ambas.
2. Nenhuma.
3. Depende do contexto.
4. Preposition at the end.

Frase 1 = Num contexto formal.
Frase 2 = Num contexto menos formal ou, simplesmente, informal.

A: "Which street did Zé say he waited 19 hours and a half for Maria on?"¹
B: "Lambaster Street 123. In front of the movie theater."
A: "Oh my God! Did she show up?"
B: "Yes. On the next day. I guess they missed the movie they had planned to see."

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¹ On which street did Zé say he waited 19 hours and a half for Maria?

Eu posso separar as preposições que acompanham o which sempre que eu quiser?

Sim.

Ou você coloca a preposição no fim ou no começo.

"Which part of the sentence should we place the preposition in?"
"In which part of the sentence should we place the preposition?"

"Which part of the sentence should we place the preposition in in?"
"In which part of the sentence should we place the preposition in?"