UCLA - Flexibility Between Physics & Aerospace Engineering | Where is Astronautical Engineering?

I was wondering how easy can I switch between Physics and Aerospace Engineering (AE).
I have been accepted to UCLA for an Astrophysics major and I have checked the UCLA class catalog.

I can see that Physics & AE have the similarities in Lower Division requirements (physics except for 17, 18L; all of Math, and Chem/Bio). However it is there is no upper division similarities at all. That means it is flexible until I am in Junior year correct? How difficult is it to transfer between Department of L&S and Department of ME & AE? Am I missing anything?

Secondly, where is astronautical engineering in UCLA. Is it only for graduate programs such as:
https://www.uclaextension.edu/eistm/Pages/engineering/astronauticalEng.aspx

Not 100% what UCLA Extension is. I am assuming it is grad programs or just extra courses.