1. One who errs in the blessings of the Shema in the morning, and instead of starting with “Yotzer or” he started with “Hama’ariv aravim”, if he has not yet finished the blessing, he should correct himself and say “Yotzer or” until the end, and finish “Yotzer hame’oros”, and with this he has fulfilled his duty. (Shulchan Aruch 59)
2. If he did not say the words “Yotzer or uvorei choshech” at all, even if he finished “Yotzer hame’oros”, since the beginning and middle were not correct, he has not fulfilled his duty, and he must start again from the beginning. Similarly, if he started correctly but finished “Hama’ariv aravim”, he has not fulfilled his duty, and must recommence. The general rule is that the most important point is to say the first few words and the ending of the blessing correctly, and if he missed out one of these, he has not fulfilled his duty. (Mishne Berurah ibid)
