There have been many film adaptations of Mary Shelley's novel Frankenstein. How do most film adaptations differ from the original text version of the story?

All of the above are true to some extent. The story of Victor encountering the monster as he chases him to the North Pole and meets Robert Walton is left out of most versions. The monster has a back story - after all, he is rejected by his "father"; therefore, there is no need to make up an additional back story. The format of the novel - the frame story - is so important because it gives several points of view, but that is often hard to create in film. Films also tend to make the monster nothing more than that - because the novel calls "it" the monster, that is often the main focus; most people do not see the monstrosity when they read the entire novel and see what Shelley put down on paper.