7.79.3 Can you answer these questions?

7.79.3.1 Overleaf citation multiply defined with A&A class file

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625901

In Overleaf, when citing a reference within the document class aa from the A&A Latex package (from the journal Astronomy and Astrophysics) and compiling with TexLive2021, I get a warning Package ... 
[bibliographies] [natbib] [labels] [overleaf] [warnings]
 

asked by bproxauf https://tex.stackexchange.com/landing/r/digest?cta=user&id=113493 1 vote

7.79.3.2 Beamer: Reserving space for video overlaya^\200\224automatically

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625748

This question is rather similar to Beamer: Reserving space for video overlay : 
For preparing a video lecture, I would like to have a frame template on which I can reserve a rectangular area, on which ... 
[beamer]
 

asked by Cameron Hudson https://tex.stackexchange.com/landing/r/digest?cta=user&id=242928 1 vote

7.79.3.3 Force ligatures with accent

https://tex.stackexchange.com/landing/r/digest?cta=question&id=625957

Latex fonts are famous (or infamous) for it tendency to use Ligatures like those in "ff","fl","fi". 
I was specting that from "f'i" but a minimal space appear. I ... 
[fontspec] [ligatures]
 

asked by Ernesto Iglesias https://tex.stackexchange.com/landing/r/digest?cta=user&id=126078 1 vote