Equations Diagrams TikZ Arrows Commutative Diagrams – Creating Diagrams with Loops in TikZCD

Question

I would like to know how we can draw this diagram in tikzcd

Those are not dotted arrows but simple ones.

You can add how we can draw an isolated point with an arrow to itself.

Many thanks in advance.

Answer 1

\documentclass{book}

\usepackage{tikz-cd}

\begin{document}
\begin{tikzcd}
    \bullet\ar[r]\ar[d]\ar[rd]\ar[loop, <->, in=170,out=100,looseness=5]&[10pt] \bullet\ar[d]\ar[loop, <->, in=10,out=80,looseness=5] \\
    \bullet\ar[r]\ar[loop, <->, in=190,out=-100,looseness=5]& \bullet\ar[loop, <->, in=-80,out=-10,looseness=5] 
\end{tikzcd}
\end{document}