I'm not sure that I get your question. generally, we put the preposition at the end, but sometimes it comes at the beginning in formal language:
Which city were you born in?
In which city were you born?
The second is decidedly more formal than the first. The preposition used depends entirely on the verb\adjective, etc, used in the question:
Who do you depend on?
On whom do you depend? (Here whom is used directly after a preposition)
Does that help at all?