Is there a delay to include call function modification in a scheduled cron task?

I´m testing my cron task.
I´m not sure but it seems to be the effect of a previous code.
So, I´m wondering when you modify you call function and you run now your cron task (I´m using WP Control) and you load a page, the code applied is not the most recent code you upload.
It´s right or wrong ?
What happens excalty, call functions are cached ?

Show different theme for admin?

I’d like to test some theme changes on my live site, but I obviously don’t want regular users seeing any errors that may arise from it. I’d like to just duplicate my theme folder and if I’m logged in as admin, then that theme is shown to me, otherwise, the old theme is shown to my users.