How do i downgrade while keeping everything?

Hey y'all! I have a late 2011 13 inch mbp currently running sequoia.

As you all know, itunes is no longer supported on sequoia. I used it for a while via the retroactive app, but it kept crashing so i sadly moved to apple music. And it too keeps crashing every time i try to create a playlist.

I NEED a music app but seems like i can't have that on sequoia. So i'm thinking about downgrading to monterey or mojave. While sequoia ran pretty well, downgrading would also make the experience smoother.

How do i do it while keeping everything as is? I also have a windows partition