I don't know if I can satisfactorily answer those questions, but I suspect the answer to all three is "no". The reason being: you can't do any of those things on the main DW site, and a Dreamhack is just your own personal "sandbox" copy of the DW code.
The advantage to using a Dreamhack is that you won't be messing with your main journal style or have to make gibberish entries in your main journal-- you can just make your test entries there where no one but you has to see them. Am I making sense? You can feel free to e-mail me if you have more questions if you prefer not to take up more comment space here.