That's pretty retarded throughout, but the bolded part is particularly funny. Even WITH a signed contract there's no way to determine that. The latter contract would have to be brought up by the interested party. Which, you know, the interested party is welcome to do at any time, instead of sending in the likes of you and Katz to make these outrageously funny arguments you make.
Now you are pretending that a signed contract cannot determine if the mutual agreement was changed or not. In case you do not know, contracts are signed to avoid any party to append additional obligations that were not part of the mutual agreement. If you were wise enough to read the book I recommended to you, instead to spell out your arrogance, you would find this:
A written offer containing all the terms of the contract, signed by the proposer, and accepted by the other party by performance on his part, is enough to enable the latter to sue under the statute of frauds. And where there is no such necessity for writing, it is optional with the parties to express their agreement by word of mouth, by action, or by writing, or partly by one and partly by another of these processes. It is always possible, therefore, that a simple contract may have to be sought for in the words and acts, as well as in the writing, of the contracting parties. But in so far as they have reduced their meaning to writing they cannot adduce evidence in contradiction or alteration of it. They put on paper what is to bind them, and so make the written document conclusive evidence against them.