Is there a Run for like, just the RPD section as leon? where it ends when you unlock the gate to leave? or a sewers run where it ends when you get on the lift at the end?

u can do this for practice. as a real category, no.
I did used to do this all the time for practice and its definitely helps. Like practicing ada section to get 2:53 or whatever.
Even though it'll never be a category/be competitive, don't let that discourage you from doing it because it can be a nice form of practice that's similar to a real run.