Does brain shape determine most of your personality, and sexual preference? and does the shape remain fixed throughout the lifetime?

Interesting question: I am unaware of any literature to suggest that brain shape has any effect of that nature. However, I hope one of the providers would be able to answer your question. Interesting thought.

No one knows yet but: A 2017 study found certain personality traits were associated with diff. brain shapes, but we don't know if personality causes brain shape or (more likely) vice versa. I doubt it determines "most of your personality" and researchers did NOT correlate it with sexual preference so we don't know and also don't know yet if it remains fixed; my guess is it can change. See https://tinyurl.com/y63tqoyc