I am confronted with my 1st ERROR as detailed below and need support in troubleshooting the issue:

"Error: Opening the cache (E:Couldn't create temporary file to work with /var/lib/apt/lists/in.archive.ubuntu.com_ubuntu_dists_bionic_InRelease - mkstemp (30:Read-only file system),E:The package lists or status file could not be parsed or opened.)"
This usually means that your installed packages have unmet dependencies.

These look like permission errors to me. Are you sure you were working as root?

Or your root partition could be corrupt. Check the startup log.

Well-formatted question btw. I wish all newbies were so informative.

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It's a bit of guesswork, but it seems to try creating a temporary file in a location that is mounted read-only. Unfortunately, the error message doesn't tell us where that is. Perhaps by listing your mounted filesystems you can detect one that is read-only though it shouldn't be.

First approach:

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Read-only filesystem is a rather significant error. Something went wrong, probably during system initialization, after POST and Grub menu selection, to prevent the root filesystem from mounting normally in read/write (rw) mode. It's also possible something went wrong during the previous shutdown, or the power was removed instead of shutting down properly.

First thing to try is rebooting, to see if it happens again. If it's repeatable, you'll need to perform a rescue boot and repair. The hard part is in determining what needs repairing. In such a case the first step is in determining where the root filesystem is and its type and attempting to check it.

How old is this installation? If brand new, it is likely to be much easier to install again than to repair.

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Thanks mrmazda! Your inference drawn was perfect! In fact, there was indeed a power outage issue and the computer did not shut down properly. The first rebooting did not resolve the issue; but a second reboot removed the error. Thanks, once again!