I'm not sure that Hero really changes very much from the beginning to the end of the play. She remains very trusting of Claudio, despite the fact that he publicly shamed her and refused to marry her at their wedding.
Beatrice and Benedick both learn that they really can trust one another and that marriage won't be such a horrible thing after all. When the play begins, they both swear they will remain single, and especially that they will have nothing to do with the other. But through the manipulations of their friends, they learn that what they wanted all along was truly marriage to one another. In addition, Beatrice learns that Benedick is truly a trustworthy man because of his willingness to fight Claudio for Hero's honor.
Claudio, I think (I hope!), has come to realize that he really can trust Hero to be faithful to him. Twice he was led to believe that she was disloyal to him (both times by Don John - come on, Claudio, catch a clue!), and both times he was shown that she really was "a jewel"!
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Benedick starts the play as someone who claims to want to be a bachelor forever, and a self-proclaimed "professed tyrant" (I.i.169) to women.
He does not want to fall in love, and prefers the life of a soldier. This changes completely however, when Benedick falls in love with Beatrice. Soon, he has forgotten all about his previous ideals, and is helplessly in love.
People change by the end of the story it is because when for instance if you take Beatrice and Benedick there love was not really there but because of Don Pedro they actually did fall in love but even at the end Benedick still mockingly said "out of pity i will marry you". and in Hero's and Claudio's case that love was not true that is because it was actually an arranged marriage and you can also see that there is a fear of being a the hored man (the man that has been cheated by his wife) in the seeane when they are in the church and about to get married Claudio turns around and insults her in front of the whole congregation and had no shame for her.
Beatrice and Benerdick have courted each other before in the past but they seperated from each other as Benerdick had apparently abandoned her. So apparently infuriated and disgusted about this, they go on for a battle of wits and skills, neither letting the other say anything without a pun or a criticism remark from the accused. It is proven when Benedick calls Beatrice a “rare parrot-teacher,” Beatrice responded in reiteration:
“A bird of my tongue is better than a beast of yours”
Even though their crude remarks are piercing, their clever, interconnected way of rebutting and sparring each other seems to signify a strong bond with each other. Beatrice also described about their relationship as a battle that she had lost. They were claiming to scorn love and have no relations with each other.
Their true love for each other still blossomed later on due to all their friends manipulations and benign tricks to make them fall in love again. They started by coming up with a schemes and deceptions to trick Benedick to believe that Beatrice likes him and their friends also did the same in return to Beatrice, making them believed they are meant for each other and they married each other
On the other hand, there is another relationship brewing- between Claudio and Hero. Even though Claudio publicly shamed and disgraced Hero during their wedding anniversary, Hero still remains loyal to him and trust him even more