Assuming this is a multi-version development environment, you can only run one instance of Windchill at a time. That goes for installation too. Shut down the existing installation. If it is running, the new one won't install. When finished installing, configure each so they don't automatically start with the server. And (if you write startup scripts), ensure both are shut down (Windchill and Apache only) before launching one of them.
Both can point to the same OpenDJ instance. Starting with 12.x, the LDAP becomes a common resource for all Windchill instances, like the mail server.
SOLR Server needs to be installed per each release. I've run multiple Windchill releases against one SOLR Server and different sets of cores. It wasn't terribly stable. Just use search criteria instead of keyword search if you don't want to install SOLR Server.
The last version-specific change to the CAD Workers was 11.x. So, CAD Workers can be common between 12.x servers if you choose a 12.x compatible WVS version, the Windchill URL is not changing, and you are only running one Windchill at a time.