"Which house does Raj live in?"
Translation:राज किस घर में रहता है?
1) "किसके घर में?" is "In whose house"
2) As a native English speaker, it sounds better (more educated) when one can construct a sentence to follow a general rule that sentences not end in a preposition.
So a sentence that sounds better (2) and follows (1) is "In which house does Raj live?"
there is no such rule, if only in prescribed grammar. no native speaker would think this sentence is wrong, people say this kind of thing all the time. so this "rule", if exists, is totally synthetic and has nothing to do with how people speak, even the most "grammatical" of people. kind of like the "rule" (more of a guideline) not to start sentences with "And"