The “Back” and “Apps” buttons on my MIL’s Samsung tablet aren’t working. Any idea if they can be turned off and back on again? Thanks in advance.

You can do a system reset, in Settings to reset everything back to default settings. Be warned though that you may lose any data stored in the memory, and have to reset / reload most of the Apps that she has added in addition to the default apps, email etc. A bit drastic, but sometimes its necessary to get the clunky Samsung tablets working properly again. I’ve had to do mine several times.