I think you keep them, though I never tried but I would assume so, as some people used to delevel to lvl 3 to take advantage of the luck skill and kill others without dropping stuff :).
If you delevl you will loose any skills that are 10 lvls higher than the lvl you delvl'd too. So if you stop at 42 you should still have your 52 skills.
so is it 10 lvls or 11 lvls that you lose your skills?
You may delevel 10 levels and still keep skills...at the 11th level you will lose skills. So if you have L52 skills, you can safely delevel to L42. Drop to L41 and you lost your L52 skills though. (Tested extensively...) :eek: