melodie
You can test hardware very easily with the Linux distributions. antiX is also wonderful because easy to use out of the box, light and provides the application having for name “Snapshot” which allows you to rebuild your own version.
In order to put up a USB stick you can install Ventoy on a usb stick then add iso images of live distributions. http://ventoy.net is quite easy to get the hang on it, and antiX is among the distributions known to boot from it.
What you might want to do is do one post per question, and solve one question at a time, to ease the learning curve. This is how I started, almost 20 years ago (once I passed the period of overwhelming and someone told me I needed to take it one problem at a time).
Then you will be able to diagnostic hardware using free software, to know what the best course of action is with a given machine, know which distribution will fit it best, how to help users, how to teach them how to use their computer with a Linux distribution and how to maintain it.
Linux in pictures:
http://www.delafond.org/roman_photos/index_en.html
😀