Now that your
poll has closed, here are the answers I was holding back:
1. You cannot mirror nor be a client to a
console running a different version of software than you are. In addition, your
fixture library version, keyboard and help languages must all be in sync as well for a client to connect to the primary. Running version 2.x and Version 3.x will definitely not connect properly (if at all) to each other. It is possible to program a show offline and save it in formats that are compatible with each other in either branch. Obviously, features that did not exist would not be available in the older versions.
2. As you've discovered, the primary development effort for 2.9.x was indeed to create 64-bit versions of the software to comply with Apple's mandate that apps change to 64-bit. We got most of it right in 2.9.0 but had a couple of bugs near the end of 2.9.0 that caused Catalina support (where Apple does a process notarization) to be delayed until 2.9.1.
Eos is not just a single executable and has many utilities and other processes it relies upon for different functions. All of these must also be 64-bit to pass notarization and it turns out that even just recompiling old code with a new compiler can introduce several new behaviours (bugs, features, featured bugs,
etc). These things all take time and test effort to ensure that we haven't broken working features just to go to 64-bit. It is just not possible to go back to older code branches and "recompile" as a 64-bit application and expect everything to work due to the complex interactions of the software.
It seems that all of the modern OS developers have an interest in deprecating support for legacy code be it for sales, vulnerability, and/or support reasons. If you were to time capsule your computer, it would run at whatever versions you had at the time, but you couldn't take advantage of new features. If you had upgraded to take advantage of new features, you might also have to upgrade to the appropriate hardware that supports those features as well. This appears to be the trade-off of the world we now live in.
It sounds like you may have been misinformed about software releases and were unaware of newer development. 2.9.2 is the
current software version of the 2.9 branch. While we are not planning any further feature releases for the 2.9 branch, we do
release fixture library updates to support newer fixtures on older consoles as well as may
release critical
bug fix versions in that branch in the future. New and exciting feature development will occur in the 3.x branch.
I hope that helps.