8.24.3 Can you answer these questions?

8.24.3.1 With twocolumns is there a macro which tells you which column is being typeset?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=640138

Apologies for not providing an MWE, but my use case is along the lines of 
\newenvironment{...}{ 
\if in first column then put something in left margin 
\else put something else in right margin 
\fi 
... 
[two-column] [multicol]
 

asked by Peter Wilson https://tex.stackexchange.com/landing/r/digest?cta=user&id=12082 Score of 2

8.24.3.2 Circle and colored-arrow in xypic

https://tex.stackexchange.com/landing/r/digest?cta=question&id=640674

I'm using \usepackage[all,cmtip]{xy} and I'd like to create a circle for $\overline{D_1^n}$, I'd like to color in red the $f\circ\pi$-arrow, I'd like also to shade the $S^n/\mathbb{Z}^2$. I inserted ... 
[color] [xy-pic]
                                                                                  

                                                                                  
 

asked by Puck https://tex.stackexchange.com/landing/r/digest?cta=user&id=244759 Score of 1

answered by Sandy G https://tex.stackexchange.com/landing/r/digest?cta=user&id=125871 Score of 0

8.24.3.3 Trying to modify the appearance of a description environment

https://tex.stackexchange.com/landing/r/digest?cta=question&id=640056

I have to do something like this but I don't know how to do it. I tried with \newcommand and \newenvironment but it seems that it's the wrong solution 
if you have any idea please tell me. 
[color] [lists] [indentation] [description] [french]
 

asked by Lowsxd https://tex.stackexchange.com/landing/r/digest?cta=user&id=267964 Score of 1

answered by Mico https://tex.stackexchange.com/landing/r/digest?cta=user&id=5001 Score of 0