Latex report displays page number is different places

Question

I am quite new to Latex and trying to make the report based on the template provided by my professor.

I am observing that latex is displaying the page number in different places such as for some page it displays the page number in the top-right corner and for some page, it displays in bottom-centre. Is this expected? Also, when the page number is displayed on the top-right corner then the chapter names appear on the top-left corner.

1. Is it possible for me to have the page number only on bottom-centre for all pages?

2. Also, why only on some pages the chapter heading is displayed on the top-left corner? Is this something to do with \documentclass[a4paper,12pt]{report} I am using?

3. Is it possible for me to have the roman numbers for contents, abstract, list of table and images? I know if I use book I can achieve this but if I use book then my images and text is getting messed up so I am using the report. Is there any possibility to achieve the same using the {report}.

The page number on bottom-centre and top-right: https://i.stack.imgur.com/hwJ1H.png

Following are the template which are provided by my professor:

  \documentclass[a4paper,12pt]{report}
\usepackage{fontspec}  
\usepackage{microtype}  
\usepackage{polyglossia}
\setdefaultlanguage{english}
\usepackage[english]{selnolig}
\usepackage{geometry}
\usepackage[usegeometry,
            margin=20mm,
            twoside=semi]

\usepackage{acronym}
    \renewcommand*{\acsfont}[1]{{\rmfamily #1}} 
\usepackage[export]{adjustbox}
\usepackage[font=small,labelfont=bf]{caption}
\usepackage{csquotes}
\usepackage{graphicx}  
\usepackage{icomma} 
\usepackage{ltablex}   
\usepackage{newfile}   
\usepackage{overpic}   
\usepackage[hyphens]{url}
\usepackage{url}

\parindent 2em         
\parskip 0.5em          

\pagestyle{headings}

%THIS IS WHERE SOME COMMON conctent added


\usepackage{hyperref}
\usepackage[a-1b]{pdfx}

\usepackage{makeidx}         
\makeindex                    

\setcounter{secnumdepth}{4}    
\setcounter{tocdepth}{4}       


\author{\dcauthorfirstname~\dcauthorlastname}
\title{\dctitle}
\date{\today}


\begin{document}
\frontmatter


\section*{\centering Acknowledgements}
%THIS IS WHERE I ADD THE Acknowledgements FROM ANOTHER FILE

\vfill
\thispagestyle{empty}
%-----------------------------
% Abstract
%-----------------------------
\section*{\centering Abstract}
%THIS IS WHERE I ADD THE ABSTRACT FROM ANOTHER FILE

\vfill
\clearpage{\pagestyle{empty}\cleardoublepage}

\pagestyle{headings}


\tableofcontents            \clearpage{\pagestyle{empty}\cleardoublepage}
\listoffigures              \clearpage{\pagestyle{empty}\cleardoublepage}
\listoftables               \clearpage{\pagestyle{empty}\cleardoublepage}

%THIS IS WHERE I ADD THE ACCRONYMS FROM ANOTHER FILE
\clearpage{\pagestyle{empty}\cleardoublepage}    
\mainmatter 
\acresetall

%---------------------------------------------------------------------------------------------------
\chapter{Introduction}
%THis is where I include the Introduction text from another file

\chapter{Conclusion}
%THis is where I include the Conclusion text from another file


\begin{appendix}

\chapter{Appendix}
\label{chap:Appendix}
%THis is where I include the Appendix text from another file

\end{appendix}

\backmatter

\printindex


\addcontentsline{toc}{chapter}{Bibliography}
\printbibliography


\end{document}

Answer 1

In report class you can get a centred page number in the page foot, and no page head using

\pagestyle{plain}

(Which is the style already used on chapter openings)

You can use

\pagenumbering{roman}

and

\pagenumbering{arabic}

To use roman or arabic numbers, setting the page count to 1 in each case.