\documentclass[10pt,letterpaper]{article}
\usepackage{graphicx}
\usepackage[left=1.00cm, right=1.00cm, top=1.00cm, bottom=1.00cm]{geometry}
\usepackage{subcaption}
\usepackage[export]{adjustbox}
%\usepackage[font=small,labelfont=bf, justification=raggedright, format=plain, singlelinecheck=false]{caption} %mettre avant subcaption pour créer une erreur
%\usepackage{hyperref} 
%\hypersetup{colorlinks,%
%	citecolor={blue}, % Change for "black" with natbib
%	urlcolor={blue},
%	linkcolor={blue},
%	breaklinks={true},
%	pagebackref={true},
%	hyperindex={true},
%}
\pagestyle{empty}
\graphicspath{{Figures/}}
\begin{document}

%%%%%%%%%%%%%%%%%%%%%% Figure 1 %%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[!h]
\centering
\includegraphics[width=.2\linewidth]{cat.png}
  \caption{Une figure}
  \label{fig:1}
\end{figure}

%%%%%%%%%%%%%%%%%%%%%% Figure 2 %%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[!h]
\centering
\includegraphics[width=.2\linewidth]{cat.png}
\qquad \includegraphics[width=.2\linewidth]{cat.png}
%\qquad \includegraphics[width=.2\linewidth]{cat.png}
%\qquad \includegraphics[width=.2\linewidth]{cat.png}
%\qquad \includegraphics[width=.2\linewidth]{cat.png}
%\qquad \includegraphics[width=.2\linewidth]{cat.png}
  \caption{Deux images, un seul titre}
  \label{fig:2}
\end{figure}

%%%%%%%%%%%%%%%%%%%%%% Figures 3 et 4 %%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[!h]
\centering
\includegraphics[width=.2\linewidth]{cat.png}
  \caption{Deux images, deux titres\label{fig:3}}
\qquad \includegraphics[width=.2\linewidth]{cat.png}
  \caption{Deux images, deux titres\label{fig:4}}
\end{figure}

Pour les figures~\ref{fig:3} et~\ref{fig:4}, il n'y a qu'un seul environnement \verb|figure|, mais deux commandes \verb|caption|.  Ceci peut \^etre utile pour deux figures qui doivent se suivre et qu'on ne veut pas s\'eparer.

\clearpage
%%%%%%%%%%%%%%%%%%%%%% Figures 5,6,7 et 8 %%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[!h]
\centering
\begin{tabular}{p{.47\textwidth}p{.47\textwidth}}
\centering\includegraphics[width=.5\linewidth]{cat.png}\newline
  \caption{Deux images, deux titres, mais c\^ote \`a c\^ote, environnement tabular  \label{fig:3new}}
& \centering\includegraphics[width=.7\linewidth]{cat.png}\newline
  \caption{Deux images, deux titres, mais c\^ote \`a c\^ote, environnement tabular \label{fig:4new}}
%\tabularnewline
% \centering\includegraphics[width=.5\linewidth]{cat.png}\newline
% \caption{trois images, trois titres, mais c\^ote \`a c\^ote, environnement tabular \label{fig:5new}}
%& \centering\includegraphics[width=.7\linewidth]{cat.png}\newline
% \caption{quatre images, quatre titres, mais c\^ote \`a c\^ote, environnement tabular  \label{fig:6new}}
\end{tabular}
\end{figure}
%\end{document}

%%%%%%%%%%%%%%%%%%%%%% Figures 9 et 10 %%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[!h] % [valign=t], + parler du package caption (essais ds préambules)+ ouvrir CTAN
\centering
  \begin{minipage}[t]{0.4\textwidth}
    \centering
    \includegraphics[width=.7\linewidth]{cat.png}
    \caption{Deux images, deux titres, mais côte à côte, environnement minipage}
    \label{fig:7}
  \end{minipage}
%\qquad
  \begin{minipage}[t]{0.44\textwidth}
   {\centering
   \includegraphics[width=.5\linewidth]{cat.png}
    \caption{...}}
    \label{fig:8}
  \end{minipage}
\end{figure}

%%%%%%%%%%%%%%%%%%%%%% Figure 11  %%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{figure}[!h]
\centering
\begin{subfigure}[b]{.3\textwidth}
  \centering
  \includegraphics[width=.7\linewidth]{cat.png}
  \caption{Sous-figure 1}
  \label{fig:sub1}
\end{subfigure}%
\begin{subfigure}[b]{.3\textwidth}
  \centering
  \includegraphics[width=.9\linewidth]{cat.png}
  \caption{Sous-figure 2}
  \label{fig:sub2}
\end{subfigure}
\caption{Une figure avec deux images, deux sous-titres, environnement subfigure}
\label{fig:test}
\end{figure}
%\newpage
\`A noter ici que l'on peut r\'ef\'erer \`a la sous-figure (\ref{fig:sub1}), ou \`a la figure elle-m\^eme (\ref{fig:test}).  
\end{document}