No, not all anime are exact replicas of the manga. Some might simplify the plot, cut out certain elements, or add new ones to make it more suitable for the animation format and the target audience.
Not all do. Some anime make significant changes to the story or characters from the manga.
In many cases, anime adaptations try to stay true to the manga, but there can be differences due to various factors like budgeting, time constraints, or creative decisions. Sometimes, it works well; other times, it disappoints fans.