scared of updating - no child themes used

Hi there! I created a site using Atahualpa theme, however, I haven't created a child theme and made changes to base code. I'm isung multi site network and I'll need to clone this site several times. It turns out that I'm afraid of upgrading to latest version and lose the changes I and if I don't, I am afraid that someday there may be incompatibilities with some plugins, for example.
I read you said that it's not necessary to use child theme with atahualpa...but can I update it without losing work already done?
Thank you