Dissertation proposal before admission: Is it possible? It seems that most universities in Europe require an outline of the planned dissertation at the application stage. I think even choosing the title of a dissertation needs a lot of dialogue between the student and his supervisor. It also requires a thorough investigation on the state of art in the targeted area. 

Is such proposal the definite proposal or it may totally be changed after the admission? Can you provide some tips for writing such proposal draft? How much time you think I should devote for such plan (at least)?
I once had to write a thesis proposal for admission to a UK university. It was explained to me that this is more of an entrance exam than an actual proposal. It is also used to gauge whether your interests lie somewhere in the vicinity of what is generally done at the department.

I don't know how other countries or universities work, but I can't imagine that anybody would hold you strictly to a proposal you wrote before becoming a graduate student. It's normal to expect that your research should be adapted along the way based on your findings, even for an experienced researcher. 

The proposal I wrote (which was successful) had to be short, so I went with the following format:


Theory so and so implies that A is true
But this other theory suggests that the converse, B, would be true 
These could be pitted against each other in an experiment involving so-and-so (details details details)


The time you need entirely depends on your knowledge of the field. It is good to invest quite some time in these things though, as they can really improve a lot the more you think about them. I'd say that it's best to try to finish it a good month before the deadline, and then take a look at it at biweekly intervals to make improvements.