I have updated original firmware (001016) with an updated version firmware 001033 downloaded from offical Samsung website and loaded via USB key (name T-GAP8DEUC).
I was now trying the Firwmare downgrade procedure before rooting the device viewtopic.php?t=4199
but when I try to set DNS manully I receive the following error (it seems like DNS 46.101.161.165 is not resolving):

and when I try firmware online upgrade, I receive the following error "Connection Failed. Error code 603. Parameter not valid. Last software is not available.":

Whant should I do?
Thanks.