OS
Can you revert back to Mojave after updating to Catalina. Many of my programs don't operate and I wasn't aware that they wouldn't until it was too late.
MacBook Air 13", macOS 10.15
It can be done to go back to Mojave but it's not that simple if you don't have a TimeMachine backup.
Which apps don't work anymore? It could be easier to update them or look for alternatives.
In the meantime make a TimeMachine backup. There always comes a moment you'll need it https://support.apple.com/en-us/HT201250