Update on the issue:

I created another temporary Yahoo e-mail account on my computer, and
using this new Yahoo e-mail account, I have full functionality using
Internet Explorer, which is good.

So the problem (which is not solved yet), but further narrowed down is:
so far on my home computer only, my original Yahoo e-mail account does
not have certain functionalities, such as, but not limited to: "Reply",
"Forward", "Move".

When I use the same Yahoo e-mail address on another browser, Firefox,
or another computer, the Yahoo e-mail address works fine.

So the problem seems to be something very specific in the interaction
between my computer Windows ME Internet Explorer 6.0, and a specific Yahoo
e-mail address.

Any solutions recommended other than re-installing my operating system?

"Here twice"