Using TM backup's
I have a few "easy" questions on using TM backup's. I've been making backups for years but have never needed to use one for back up. I'm on a 2017 i-Mac(4K), Catalina 10.15.7, using a WD USB 2TB back up drive.
My questions are:
1) Can older backup's made with older OS's be used for backup. In particular if I upgrade to Big Sur will back up's made with Catalina work with Big Sur?
2) How can I demonstrate that my existing backups are ok before moving to BS?
3) Can I re-start in Safe mode using recent BU files without doing a full erase of my main HD?
I know I need to do a clean install since I have migrated from two systems over the last 14 years. I think I have had lot's of kernal attacks resulting in app freezes, force quits)
Bill S.
iMac 21.5″ 4K, macOS 10.15