7.72.3 Can you answer these questions?

7.72.3.1 Receiving Package xkeyval Error: `x' undefined in families `blx@opt@name'

https://tex.stackexchange.com/landing/r/digest?cta=question&id=622725

I am using TeX-Live on a Mac with macOS 11.6.1 with the latest TeX Live version. All packages are updated today. 
When I am building my LaTeX document with \printbibliography I receive the following ... 
[bibliographies] [xkeyval]
 

asked by Daniel Aldus https://tex.stackexchange.com/landing/r/digest?cta=user&id=125216 1 vote

7.72.3.2 DocumentClass-Independent Table of Contents (eToC)

https://tex.stackexchange.com/landing/r/digest?cta=question&id=622703

I want to create a local table of contents, and am currently using etoc. I noticed that the formatting is largely dependent of the documentclass. 
Below is a screenshot for the article document class ... 
[tocloft] [minitoc] [etoc]
 

asked by Otanan https://tex.stackexchange.com/landing/r/digest?cta=user&id=246278 1 vote

7.72.3.3 Extra \endgroup error after transforming \documentclass article  into \documentclass revtex4-2

https://tex.stackexchange.com/landing/r/digest?cta=question&id=622533

Can you please help me identify what is wrong with my coding? I've searched online for solutions but I couldn't find a working one. Before, I used article for my \documentclass to complete my thesis. ... 
[errors] [revtex] [documentclass]
 

asked by Azmadi M https://tex.stackexchange.com/landing/r/digest?cta=user&id=256688 1 vote