AFter updating to macOS Catalina, old 32-bit apps will not longer work. If you have an old 32-bit app, then before updating, you should update your app or switch to a new one. Most apps have newer versions that professionals should consider buying. If you are using the app for casual purposes, then consider getting a modern alternative to apps like Microsoft Word or Adobe Photoshop. These will be cheaper or free, and will probably be much better than using an old outdated pro app. You can also keep an old Mac around to run 32-bit apps. Experts can partition their drive, use an external drive, or a virtual machine to run Mojave or earlier in some situations.
WHen macOS Catalina comes out this fall, iTunes will be replaces with Music, Podcasts and TV apps. This leaves many people wondering what will happen to their iTunes puchases, media and how they will sync their iOS devices. The transition should be seemless for all, with many just experiencing the equivalent to an app name change from iTunes to Music. Syncing will move to the Finder. Changes to some aspects, like ringtone syncing, is unclear.