Stupid upgrade questions

Hi I just completed an upgrade on my production box from 4.4.3 to 4.4.9 which went fine, I backed up all the relevant bits (templates,theme,etc).

However I have a few dumb questions:

Whats the difference between the master branch and the 4.4 branch? I had to go to the master branch to grab the record-messages script I worked on. Is master bleeding edge nightly type stuff?

My next step is upgrading Freeswitch. Is there a magic combination of Freeswitch, Fusion, and OS version? Are there versions that we should steer clear of? I'm probably going to go to Freeswitch 1.10, and leave myself at Debian 9.8. Is that cool? I'm going after stability as opposed to bleeding edge feature upgrades.

I'm kind of a (if its working) don't upgrade unless there's a security issue type of guy, but I wanted to go through the upgrade process at least once before going into full on production.

With all that said it might be nice to have a distro with all these moving parts locked in together..
Master branch (currently 4.5.x)is the active development branch. Changes can and often occur multiple times per day.

Stable branch will usually only receive security fixes after released. Since master branch is very near the next release, 4.4.x will receive fewer updates. Many security fixes currently in master will never make it to 4.4.

When a new “stable” release is made, the current code at that moment of master is what is used. Then a new master branch is created for future development.

As of right now, Freeswitch 1.10.1 is working well for many people. The main Freeswitch version to steer clear of was 1.8.5 due to a NAT bug. In Freeswitch 1.10 the postgressql code has been removed from core and is now a module. If installing a new server the fusion install scripts will take care of things, but if upgrading an existing version of Freeswitch you will need to install the new module for Fusion to work.