Thanks for the quick response. The issue I have is that the original site was my first site with Theme X and I didn't use a child theme.
I have tried to upgrade to the latest Theme X but the the site breaks because of really old modifications. Rather than fix these issues, which could take a while as would have to remember what I did, I want to do a fresh install in a development environment of the latest theme x and create a copy of old site using the child theme . Is that possible?
Once I am happy the new site works and i make it live I could then upgrade to pro, does that make sense and is that possible?