What does Frankenstein learn throughout the course of the novel and how do his plans change?
One could argue that Victor Frankenstein has learned nothing from his experiences reanimating dead tissue and creating a living being from which he immediately recoils. Nor did he learn from the tragic death of his young brother. Mary Shelley's Gothic novel presents a fascinating contemplation of the nature of man and the sin of assuming a "god complex." Early in Frankenstein; Or, the Modern Prometheus, Shelley's protagonist regales his host and temporary savior, Robert Walton, with the history of his efforts at creating life. Frankenstein's comments are filled with messianic fervor and only intermittently does he question the wisdom of his endeavors. He is obsessed with both his pursuit of the ability to create life and with his status among other living, thinking beings. As he tells Walton, "A new species would bless me as its creator and source; many happy and excellent natures would owe their being to me."
Frankenstein can be said to have learned from his ill-considered efforts, as he recoils in horror from his creation. He learns later that the creature responds to being rejected by killing Victor's precious younger brother. He quickly learns to regret his experimentation. He remains throughout, however, obtuse. He eventually brings more suffering upon himself and those to whom he is closest, including his friend Henry Clerval and his beloved bride Elizabeth.
Perhaps the best evidence of Frankenstein's failure to learn from his past and from his mistakes is his ill-fated decision to destroy the female he was creating for the "wretch." Having listened to the creature's protracted story of its life, especially his/its experiences with De Lacy and his children, Victor agrees to create a female companion for his initial creation, who promises to live remotely in the countryside far from human civilization. This eminently reasonable decision, however, is followed by Victor's sudden decision to destroy the female—an act that leads directly to Elizabeth's murder.
In conclusion, Victor Frankenstein makes a series of bad decisions that result in the deaths of his brother, William, Justine, Henry Clerval, and Elizabeth. It is questionable whether he learned from his mistakes. He did learn, however, not to play God.
The existing educator answer gives a number of excellent points about the various ways in which Frankenstein brings about his own destruction and the destruction of those around him, and yet this does not actually make him alter his course—he is determined to be lord over this being he has created, and will not allow it to guide his decisions, even when he sees that it is not the pliant son he had envisioned, but a creature with its own needs, desires, motivations and angers. "I WILL BE WITH YOU ON YOUR WEDDING NIGHT," the Creature famously says, demonstrating a strength of will and a capacity for (we may feel, justified) revenge which Frankenstein had not anticipated. Still, Frankenstein makes no attempt to reason with the Creature or really to help it; he wants to be a god over it, and indeed destroys the bride he had created for it in the feeling that the Creature does not deserve it. Frankenstein is sure that Frankenstein is right about everything.
We can see this clearly in the language Frankenstein uses in speaking to Walton of his endeavors. He knows he is reaching the end of his life, but the "evils" that have led him to it he describes as "great and unparalleled misfortunes" which he has "suffered." They are "misfortunes," and Frankenstein tells Walton that "nothing can alter my destiny." As far as Frankenstein is concerned, we can see from this passive language that he does not, even now, believe himself to have been the agent or instrument of his own misfortunes. He has convinced himself that "destiny," rather than his own bad decisions, have led him to where he is now, at the end of the world and awaiting the Creature's arrival. Surely there could be no better evidence of how completely Frankenstein has failed to learn anything from what he has done, suffering under this enormous sense of self-removal from his own actions and unable to take any responsibility for what has happened. Frankenstein believes he is "destined" to be here: this, more than anything else, seems to indicate that if he could live his life again, he does not believe he could change anything to alter how he ends up.