I don't think he wants to restore his IMEI. The reason why he changed his IMEI in the first place was because that IMEI was blocked, and only worked on a certain network. Restoring iMEI definitely is not illegal. Changing it or using another models IMEI is.
Firmware upgrade won't change his 0000000000000 IMEI to an original one.
just want to put imei code back to normal but have phone to work on any network or just to work on voda.but i am strugglng to do it with the nemesis software