Mouse left click text highlight no longer copies it

Mint Cinnamon 18.3. It used to work, that in addition to right clicking the highlighted text and using <Ctrl-C>, a second way to copy highlighted text was to just left-click and scan it. Pretty cool that it gave 2 usable ways <Ctrl-V> or mouse right-Click to "Paste" 2 stored selections. I do not know what caused it to stop functioning, maybe during an Update Manager Update. If this is a known problem, how do I fix it?

Also, (less important), in Terminal I use up arrow history twice before shutdown for UpTime and fstrim. How do I delete (or selectively delete) the (lengthy!) different undesireable history displayed with a keyboard's UpArrow? Terminal Help was NO help.

Thanks in advance.