1) One who recites the Shema backwards (meaning that either the words or the verses were not recited in the correct order) has not fulfilled his duty. (Shulchan Aruch and Mishne Berurah 63)

2) However, if he changed the order of the paragraphs (e.g. he recited “Vayomer” first followed by the other paragraphs), he has fulfilled his duty, as in the Torah the paragraphs are not written in the order that Chazal decreed that one should say them during the service. It follows that even though they decreed that they should be said in this order, if he recited them in a different order, he has nevertheless fulfilled his duty. (ibid)