Page numbering of preliminary pages in thesis

This is a revision of your MWE (which did have a problem).

% pagenumberprob.tex  SE 547685

\documentclass[12pt, a4paper, twoside]{book} % deleted open=right

\usepackage[margin=2.5cm,left=4cm, includefoot]{geometry}
\usepackage{graphicx}
\usepackage{rotating}
\usepackage[title]{appendix}
\usepackage{pdfpages}
\usepackage[nottoc,numbib]{tocbibind} 
\usepackage{caption}
\usepackage[sc]{mathpazo}
\usepackage{afterpage}
\usepackage[T1]{fontenc}
\usepackage{multirow}
\usepackage{emptypage}
\usepackage{amsmath}
\usepackage{hanging}
\usepackage{lipsum}
\usepackage{fancyhdr}
\usepackage{adjustbox}
\usepackage{diagbox}
\usepackage{notoccite}
\usepackage{fancybox}
\pagestyle{fancy}
%\fancyhead[LO]{\nouppercase\sectionmark}
\fancyhead [R]{\nouppercase\leftmark}


\fancyhead[L]{}
\def\changemargin#1#2{\list{}{\rightmargin#2\leftmargin#1}\item[]}
\let\endchangemargin=\endlist 
\usepackage{nomencl}
\usepackage{makeidx}
\usepackage{pdflscape}
\usepackage{rotating}
\makenomenclature
\usepackage{dblfloatfix}
\usepackage[font=footnotesize,labelfont=bf]{caption}
\usepackage{amsfonts}
\usepackage{cite}
\usepackage{filecontents,notoccite}

\usepackage{multirow}
\newcommand\Tstrut{\rule{0pt}{2.8ex}}        
\newcommand\Bstrut{\rule[-1.5ex]{0pt}{0pt}}
\usepackage{multicol}
\linespread{1.3}
\usepackage[utf8]{inputenc}
\usepackage{lastpage}
\usepackage{afterpage}
\newcommand\blankpage{%
    \null
    \thispagestyle{empty}%
    \addtocounter{page}{-1}%
    \newpage}
\usepackage{marvosym}
\usepackage[hidelinks]{hyperref}
\usepackage{afterpage}
\usepackage{tikz}
\usetikzlibrary{calc}


\begin{document}
\frontmatter
\begin{titlepage}
Title is xxx
\end{titlepage}

\setcounter{page}{0} % PW added this
\chapter*{}
%\input{dedication}
Dedicated to ...

\chapter*{Acknowledgement}
%\input{acknowledgement}
Acknowledging ...
.............
...........
\tableofcontents
.............
\mainmatter
\newcommand*\Newpage{\newpage\null\thispagestyle{}\noheader\newpage}
\mainmatter
\chapter{XXX}
%\input{XXX}
The chapter's text

\end{document}

The significant change I made was

\end{titlepage}
\setcounter{page}{0} % I added this
\chapter*{}
Dedicated to % instead of \input{dedication}

which then makes the page number of the dedication be "i", which is what you appear to want.

If you had processed your MWE it would have come up with the notice that the global option open=right was unused; there is no such option for the book class, the default is that chapters start on righthand pages.

If you don't want any distinction between preliminary pages and main content you can remove the \frontmatter and \mainmatter commands.

PS: when you upload a source code put 3 grave accents (```) on the line before and after and specify it's a tex source, example:

```tex
code here
```