Informal Questions??
 

These is the book for who?
You want to go where?
He wrote that book for whose movie?

Can we use these questions to ask in the real life?
Do they sound bad?

Re: Informal Questions??
 

Notice the mistake in the first question -
Correct - This is the book for who?

Apart from that, there's nothing grammatically wrong with the questions, but they would only be used in a particular context - if the speaker hasn't understood what was said, doesn't understand, or is very surprised by it.

1) If speaker B doesn't understand because she doesn't hear (XXX is the word she doesn't hear):
A : I want to go to XXXX for my holidays-
B : Sorry - you want to go where?

2) If the speaker doesn't understand because she has never met the informatuion before (in this case, she has never heard of Rendola)
A : I want to go to Rendola for my holidays
B : You want to go where?

3)If speaker B is surprised by what was said - ie doesn't understand why the speaker would say such a thing. (Here, B knows there's a war on in Lizbikistan)
[i]A : I want to go to Lizbikistan for my holidays.
B : You want to go where? [i]

All the questions would have rise-fall intonation on the final word - probably low rise on (1), higher on (2) and still higher on (3).

So it's not that the questions are informal, but that they are used to express a particular "extra" meaning : lack of understanding.