Your dream is rich with symbolism and seems to reflect various aspects of your life, particularly concerning your academic journey and feelings related to your past experiences.

1. Returning to Elementary School: Dreaming about being back in elementary school, especially as a top-ranked student, may signify a longing for a time when things felt simpler or more successful. It could represent nostalgia for your childhood and the achievements you had during that period, possibly highlighting a desire to reclaim that sense of accomplishment as you navigate your current situation in architecture.
2. The Beautiful Girl and the Connection: The presence of your cousin's classmate, who is now studying architecture, may symbolize a connection to your own aspirations and possibly your feelings of comparison or competition regarding your academic choices. This could reflect your subconscious thoughts about your current academic path and how others are progressing in theirs.
3. The Math Test and Notes: The math test could symbolize a test of your knowledge or capabilities, especially in relation to your studies and career. Using old notes suggests you may feel a need to rely on past knowledge or experiences to navigate your current challenges. It might also indicate anxiety about your academic performance or feeling unprepared.
4. The Teacher's Punishment: The violent imagery of the teacher punishing a student can indicate feelings of fear, control, or anxiety regarding authority figures in an educational setting. This may reflect your stress or worry about consequences for failure or mistakes in your own academic life. The act of deep-frying and eating part of a body may symbolize a sense of violation or the consuming nature of educational pressure. It could suggest feelings of being overwhelmed or 'consumed' by your academic environment.

Overall, your dream seems to reflect a mix of nostalgia, anxiety about your academic journey, and possibly feelings of comparison with others in your field. It might be helpful to explore what aspects of your studies bring you joy and how you can reconnect with those feelings, possibly allowing you to move forward in your architecture path with renewed focus and motivation.