is real dat more like achiever? or topscore
The interface looks almost identical to what's provided from the DAT Tutorial link on http://www.ada.org/dat.aspx.
P.S. Some q's require that you fully scroll through them whether it be the choices or paragraphs in order to proceed to the next q even if you've selected a choice.
are there "mark" button for each question?
Yes
can we see if all the questions were answered or not?
Yes, but after going through all the q's. Though I would advise you not leave any questions unanswered. Guess, mark, and move on. You also have the option to review only what you have marked.