doing medical school in either Hungary or Slovakia, any issues entering either country after giving 21 day notice or RSO passport stamp?

Hello all I will be looking at doing medical school in either Slovakia or Hungary, in order to practice (neurology) in Germany.  I would need to get an extended schegen visa (long stay visa D)  and I will be going as a national of my birth country as I have dual citizenship. My only issues is either country turning me away after I give the 21 day notice even though im going with my birth country’s passport.  I am level 1 and my conviction was annoying or molesting a child, Ive never been given any notice that I need the stamp however Im not going to risk it and thus will get it.