\documentclass{book}
\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage[gen]{eurosym}
\usepackage{textcomp}
\usepackage{graphicx}
\usepackage{etoolbox}
\usepackage{titleps}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{imakeidx}
\usepackage{embrac}
\usepackage{expl3}
\usepackage{tabularx}
\usepackage{float}
\usepackage{babel}
% use hidelinks to remove boxes around links to be similar to Texinfo TeX
\usepackage[hidelinks]{hyperref}

\makeatletter
\newcommand{\Texinfothechapterheading}{}
\newtitlemark{\Texinfothechapterheading}%
\newcommand{\Texinfoheadingchaptername}{\chaptername}
\newtitlemark{\Texinfoheadingchaptername}%
\newcommand{\Texinfosettitle}{No Title}%

\newcommand{\Texinfounnumberedchapter}[1]{\chapter*{#1}
\addcontentsline{toc}{chapter}{\protect\textbf{#1}}%
\renewcommand{\Texinfothechapterheading}{}%
\chaptermark{#1}%
}%

\newcommand{\Texinfounnumberedpart}[1]{\part*{#1}
\addcontentsline{toc}{part}{\protect\textbf{#1}}%
}%

\newcommand{\Texinfounnumberedsection}[1]{\section*{#1}
\addcontentsline{toc}{section}{\protect\textbf{#1}}%
\sectionmark{#1}%
}%

\newcommand{\Texinfounnumberedsubsection}[1]{\subsection*{#1}
\addcontentsline{toc}{subsection}{\protect\textbf{#1}}%
}%

\newcommand{\Texinfounnumberedsubsubsection}[1]{\subsubsection*{#1}
\addcontentsline{toc}{subsubsection}{\protect\textbf{#1}}%
}%

\newcommand{\Texinfochapter}[1]{\chapter{#1}
\renewcommand{\Texinfothechapterheading}{\Texinfoheadingchaptername{} \thechapter{} }%
}%

% no index headers
\indexsetup{level=\relax,toclevel=section}%
\makeindex[name=vr,title=]%

% redefine the \mainmatter command such that it does not clear page
% as if in double page
\renewcommand\mainmatter{\clearpage\@mainmattertrue\pagenumbering{arabic}}
\newenvironment{Texinfopreformatted}{%
  \par\GNUTobeylines\obeyspaces\frenchspacing\parskip=\z@\parindent=\z@}{}
{\catcode`\^^M=13 \gdef\GNUTobeylines{\catcode`\^^M=13 \def^^M{\null\par}}}
\newenvironment{Texinfoindented}{\begin{list}{}{}\item\relax}{\end{list}}


% this allows to select languages based on bcp47 codes.  bcp47 is a superset
% of the LL_CC ISO 639-2 LL ISO 3166 CC information of @documentlanguage
\babeladjust{
  autoload.bcp47 = on,
  autoload.bcp47.options = import
}
% used for substitutions in commands
\newcommand{\Texinfoplaceholder}[1]{}

\newpagestyle{single}{\sethead[\Texinfothechapterheading{}\chaptertitle{}][][\thepage]
                              {\Texinfothechapterheading{}\chaptertitle{}}{}{\thepage}}

% braces are upright in italic and slanted only in @def*
% so it is turned off here, and turned on @def* lines
\EmbracOff{}%

% allow line breaking at underscore
\let\Texinfounderscore\_
\renewcommand{\_}{\Texinfounderscore\discretionary{}{}{}}
\renewcommand{\includegraphics}[1]{\fbox{FIG \detokenize{#1}}}

\makeatother
% set default for @setchapternewpage
\makeatletter
\patchcmd{\chapter}{\if@openright\cleardoublepage\else\clearpage\fi}{\Texinfoplaceholder{setchapternewpage placeholder}\clearpage}{}{}
\makeatother
\pagestyle{single}%


\selectlanguage{ja}%

\begin{document}
\label{anchor:Top}%
\selectlanguage{ja}%
\Texinfochapter{{ja}}
\label{anchor:chapter-ja}%

In japanese. See \hyperref[anchor:chapter-ja]{\chaptername~\ref*{anchor:chapter-ja} [chapter ja], page~\pageref*{anchor:chapter-ja}}.

\noindent\begin{tabularx}{\linewidth}{@{}Xr}
\rightskip=5em plus 1 fill \hangindent=2em \hyphenpenalty=10000
\texttt{BBB \EmbracOn{}\textnormal{\textsl{CCC}}\EmbracOff{}}& [Instance Variable of \texttt{AAA}]
\end{tabularx}

\index[vr]{BBB of AAA@\texttt{BBB\ of AAA}}%

\selectlanguage{en}%
\Texinfochapter{{en}}
\label{anchor:chapter-en}%

In english. See \hyperref[anchor:chapter-ja]{\chaptername~\ref*{anchor:chapter-ja} [chapter ja], page~\pageref*{anchor:chapter-ja}}.

\noindent\begin{tabularx}{\linewidth}{@{}Xr}
\rightskip=5em plus 1 fill \hangindent=2em \hyphenpenalty=10000
\texttt{BBB \EmbracOn{}\textnormal{\textsl{CCC}}\EmbracOff{}}& [Instance Variable of \texttt{AAA}]
\end{tabularx}

\index[vr]{BBB of AAA@\texttt{BBB\ of AAA}}%

\selectlanguage{fr-FR}%
\Texinfochapter{{fr\_FR}}
\label{anchor:chapter-fr_005fFR}%


\noindent\begin{tabularx}{\linewidth}{@{}Xr}
\rightskip=5em plus 1 fill \hangindent=2em \hyphenpenalty=10000
\texttt{BBB \EmbracOn{}\textnormal{\textsl{CCC}}\EmbracOff{}}& [Variable d'instance de \texttt{AAA}]
\end{tabularx}

\index[vr]{BBB of AAA@\texttt{BBB\ of AAA}}%

\selectlanguage{de}%
\Texinfochapter{{de}}
\label{anchor:chapter-de}%

\selectlanguage{pt-BR}%
\Texinfochapter{{pt\_bR}}
\label{anchor:chapter-pt_005fBR}%

In brazilian. See \hyperref[anchor:chapter-ja]{\chaptername~\ref*{anchor:chapter-ja} [chapter ja], page~\pageref*{anchor:chapter-ja}}.
\end{document}
