After neglecting a Concrete5 site (I think it was at 5.6.something?) for a few years I tried to login today and hit '500' errors. Entries in logs seemed to mention PHP a lot.

I worked with tech support for my hosting company and their remedy was to ratchet back the PHP version for the site to PHP 5.6 (from PHP 7.3). This restored functionality and I can log in and use pages and the dashboard with no trouble so far, but of course I want to get it up to date.

A couple of other data points to help frame my questions on the update...

-- the site was built using a purchased them. It is no longer available which may mean
it is not fully supported on later releases of Concrete 5 -- I cannot say for sure

-- the site was about 40% complete, and I would like to preserve the blog posts, graphics/pics content and such, rather than start over

My questions:

1. Is it pretty safe to update all the way to Concrete5's latest version now?
2. Does upgrading the Concrete5 CMS automatically 'update' all PHP scripts the site
generates which would allow me to now change the PHP version for this site back to
7.3 or 7.4? Or, could the purchased Theme and various blocks used from that theme
be left untouched by the Concrete5 update and still need the older PHP?
Thank you for any replies or pointers to a resource I may have missed that covers this 'neglect' scenario.