Texas agents I need some input

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My agent has put a contract together for me to sign so that we can submit to the listing agent who is also the owner of the subject property in which I plan on purchasing. He sent me the contract to sign but he also sent an amendment to be signed with all of the requirement I wish to have met (Repairs to the fence, cellar door, and things of that nature). I was under the impression that an amendment was only necessary after the contract has been executed to add changes to the original contract. 

After signing both of these contracts could the seller refuse to sign the amendment and just sign the contract making it a valid contract and I not be entitled to anything which was listed in the amendment? 

Thanks for the help in advance.