Jack's iMac runs El Capitan, and his iMovie and Garage Band have stopped working. He has been told he has to upgrade to get them working back. But he's hesitant. Leo says that it's OK and you should upgrade. Apple isn't like Windows. You can safely go to Mojave, or at least High Sierra. Why did your apps stop working? That's a puzzle. Maybe your graphics card is too old? Or Apple may have just broken the connectivity. Upgrading to Mojave though is important for security reasons.
Charles wants to know the best way to set up Time Machine on his Mac with macOS Mojave. Leo says that in the new OS, there is a new APFS file system, and there have been backup issues with Time Machine and others. He may need to use an external drive formatted with the old HFS file system. That will insure that if his internal drive dies, his backup is secure. Leo also recommends not using Time Machine as his primary backup system. He should make an image backup with SuperDuper.
Brett just updated to OSX Mojave and hangs up on the login screen. Leo says clearing the PRAM or parameter ram can sometimes solve issues like this. Also, reboot with CMD R and that will enable you to reinstall the OS. Maybe it wasn't updated properly. If that doesn't work, Leo recommends making an appointment at the Genius Bar in the Apple Store.
Chatroom says to boot into safe mode, press and hold the shift key, and it will install the absolute minimum. If it works OK after that, then there's an app that isn't compatible that's hanging things up.
Sarah wants to know if she should upgrade to Mojave with her eight year old laptop. Leo says that if Apple lets her, then she should. Since she can run High Sierra, there's a good chance she will be able to. If it's not compatible or really makes her Mac sluggish, Apple probably wouldn't let her.