Yep GMATPrep doesn't give Official Explanations and it doesn't show ur score again.
Also I found that the software is superbuggy. Once I finished the test and did not close the software properly... Next time I open the test for review - I saw completely different questions and it says I got 33/37 questions wrong in Quant.
My suggesiton would be to search the same question in GMATClub. Most of the time u will see that the question would be posted here with great explanations!
"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."
- Bernard Edmonds