In the USA, suppose party A offers a contract to party B, who signs and returns said contract to A. The contract is a single document that has a few "sections" that each have a place to sign to show acceptance of that "section".
Now suppose that before any material action is taken by either party to proceed with the contract, A offers B what is essentially the same contract but with some minor amendments (e.g. change of start date), which B then signs and returns to A. Fullfilment of the contract proceeds on both sides using the amended terms (eg the actual start date of the contract is the start date as per the amended version).
Does the signed copy of the second version of the contract override/replace the first completely?
More specifically, suppose B initially opted to approve/accept a particular section in the first version, but decided not to opt for that section in the second version and so did not sign that section and further suppose that A did not notice the change in acceptance. Much later, after a lot of work has been done and delivered by both parties, A asks B to comply with the particular section, but B points out to A that B didn't accept that particular section in the second version and B refuses to comply.
Can A compel B to still accept the terms of the particular section because it was accepted in the first version and that section of the contract didn't change?
Or does the issuing and signing of a second version open the door to B accepting the sections differently, especially given that the behavior of both parties aligned with the second version - both A and B started fulfilling their obligations on the amended start date.
The section is question does not affect the way in which the main part of the contract is fulfilled. For example, it might be the notice period required to terminate the contract without penaltya, or similar "exit" terms that wouldn't be realized until B wanted to leave the contract.