About the compatibility story...

My early 90s experience was different, I wrote my bachelors thesis with WinWord 2.0a originally, then after switching universities for my masters degree they made it clear that they would expect me to use LaTeX, so as a learning exercise I re-did the complete thesis using LaTeX (somewhere around the switch from 2.09 to 2ε).

WinWord could already no longer process it properly when WinWord 6.0; the version right after 2.0a, came out.

The LaTeX version worked all the way until late 1999, when due to a series of mishaps the source was lost and I was left with only the PDF result, which I still have. (Generating PDF from Word documents on the other hand was basically unheard of back in the 1990s ...)

I also still have a few smaller texts I've written after the 1999 backup disaster, and these I can still process using current LaTeX versions.