Dennis' 2011 iMac is showing lines on a white screen. Leo says it could be a failed monitor, or even the cable that connects to your monitor has failed. The OS may have been corrupted as well. Try booting into recovery mode. CMD+R. That will bypass the loading of the OS and will allow you to reinstall the OS. You can also try target display mode. If the problem persists, the Mac needs replacing., because it'll cost too much to fix.
Kathleen recently updated to the latest Zoom, but her friend can't update because she doesn't know the password to her Mac. What can she do? Leo says there are about 5 ways to reclaim your login password on an Apple computer. You can find instructions on Apple's Support site - Look for HT202860. In recovery mode, there's also a reset password command. That's probably the easiest option.