Twofold question about being unable to get signal to Audacity using Mojave. Other options or am I able to revert to High Sierra using time machine?

Recently I went back to do some work on some older sound recordings I made with Audacity while using High Sierra as my OS. I was trying to use my external mixer through the USB port to record (as I always had) some additions and found that my laptop (late 2012 MacBook pro) would no longer recognize my mixer or get any signal whatsoever. I can see signal when I go to System Preferences>Sound>Input and select USB CODEC but I'm not getting signal recognition when I'm using Audacity. After a little research I see that my Mac doesn't play well with some programs and hardware using Mojave that it did while using High Sierra. I tried going to System Preferences>Security>Privacy and allowing audacity to control my computer but to no avail. I like Mojave in every other respect but if I can't get it to work with my older recordings I'll be required to revert to the older OS to continue my work in that particular idiom.

So my question is twofold:

1) Have I exhausted all attempts to get Mojave to play nice with Audacity?

2) If so, can I revert to High Sierra using time machine?

If it matters, my external mixer is a Berringer Xenyx Q1202 USB console.