RE: Will 8.5.11 still work OK in 5.0.3?
Sorry, I have no way of knowing. I do not back test old versions of Connections against newer versions of WP. Only the latest version of Connections is supported. I maintain support for three major version backwards for WordPress. For example, the latest version of Connections is 8.37 and is compatible with WP 4.7.12 and newer (4.7.12, 4.8.x, 4.9.x and 5.0.x).
RE: Will 8.3.7 work in WP 4.9.9?
Same answer as my previous.
RE: If I completely rebuild the site, can I easily get the data out of my old site into the latest version 8.3.7?
Hmmm… CSV Export was added in the 8.5 and had some tweaks thru 8.5.9 with other tweak in even newer versions. So, if you have 8.33.7 installed, the way to get data out would be thru a tool such as phpMyAdmin usually found in the web host control panel.
Not sure if this helps, but I hope it does!
