Well just have to wait and see what vadll says about it.
I have wrote email to Vadll and he reply this:
"You can do as you want to."
But I have changed the "Market Setting" to US under 4.3.4 fw and it accepted and 25 km/h limit raised to 32 km/h succesfully without any error code. ( I have tried it by short biking)
So I think Markus Schlegel the eMax developer was wrong when wrote me that market setting changing works only from 4.5.1 FW version.