Hello.

If a unit enters a hex with razor wire is it fatiuge or only it must stop but still can shoot?

It's movement immediately stops and the squad is fatigued. I believe that units attacking from razor wire, attack at half firepower, therefore the squad would immediately be fatigued even if you had declared a move and shoot. The reason for this is because you can not half a squads firepower twice which you would have to do for the move and shoot and then for attacking from the razor wire.

Thanks you very much.