Lets assume that my iphone 5c gets stolen. If the person who has the icloud account wipe all the data (they dont block the phone just wiped) will it be able to get the factory definitons like its a new phone? so if the thief activated the phone we will not get asked by the icloud account password and id?
If your iPhone is stolen and has FindMyiPhone turned on the thief would need your iCloud password in order to disable it. The thief could wipe the phone by putting it into DFU mode, but upon trying to access the phone they would run into the problem of still having to input the iCloud password into the phone so that they are able to access it as it is still registered in Apple's data base as being connected to your account.
So yes the phone can be made to go back to its original state by recovery, but no it will not be able to be activated as long as they do not have your iCloud password.