Trying to link my old gamecenter to an apple id because it needs to be updated with one, but it is not allowing me to

Trying to link my old gamecenter to an apple id because it needs to be updated with one, but it is not allowing me to use an existing acount, because it is already linked to a game center, and with i a new account, after I accept the terms and conditions, its gives me a message saying "Could not update account, Needs a minimum of 3 valid security questions and answers for secondary authentication." I have tried creating an account before hand, but when i try it it says that an account is already linked to it.