Numbering of theorems, lemmas, definitions, examples, etc for thesis

Question

I am trying to work on the numbering of the theorems/definitions/lemmas etc., and I have some problems with the numbering.

I would like the theorems, propositions, corollaries, definitions, conjectures, examples to follow the same numbering, and to reduce the numbering. For example, in my code below, the stuff goes as follows:

Chapter 1

Addition

1.1 Basics (SECTION)

Definition 1.1

Theorem 1.2

Theorem 1.3

Example 1.4

1.1.1. Some tips (SUBSECTION)

Definition 1.5

1.2 Advanced stuff (SECTION)

Definition 1.6

But how would I get it to be like this below?

Chapter 1

Addition

1.1 Basics (SECTION)

Definition 1.1.1.

Theorem 1.1.1.

Theorem 1.1.2.

Example 1.1.1.

1.1.1. Some tips (SUBSECTION)

Definition 1.1.2.

1.2 Advanced stuff (SECTION)

Definition 1.2.1.

We have used the following environment:

\documentclass[12pt,a4paper,oneside]{mnnit}
%\documentclass[a4paper,12pt,oneside]{thesis}
%\chapapp{Chapter}
\usepackage{titlesec}
%\renewcommand{\thechapter}{\arabic{chapter}}
%\titleformat{\chapter}[display] {\Large} {{Chapter~}\Large\thechapter}
%{2ex}
%{}
%[]
\usepackage{amssymb}
\usepackage{anysize}
\usepackage{epstopdf}
\usepackage{epsfig}
%\usepackage{graphicx}
\usepackage{float}
\usepackage{longtable}
\usepackage{lscape}
\usepackage{llncsdoc}
\usepackage{mmm}
\usepackage{multirow}
\usepackage[toc,page]{appendix}
%\usepackage{pxfonts}
\usepackage{rotating}
\usepackage{tabularx}
\usepackage{epsfig,float}
\usepackage{cases,textcomp, amssymb, amsmath}
%\usepackage{wrapfig}
%\usepackage{pifont}
\usepackage{psfrag}
\usepackage{color}
\usepackage{url}
\usepackage{enumitem}
\usepackage{mciteplus}
\usepackage{amsfonts}
\usepackage{enumitem}
%\usepackage{hyperref}
\usepackage[colorlinks,allcolors=blue]{hyperref}
\usepackage{amsmath,amssymb,array,longtable,wallpaper,graphicx,epsfig,subfigure,float,booktabs, pdfpages}
%\usepackage{rotating,setspace,enumerate,morefloats,xcolor,threeparttable}
\usepackage[left=1.3in,right=1.2in,top=1.4in,bottom=1.35in]{geometry}
%\usepackage{amsthm}
\usepackage{lipsum}
\usepackage{tikz-cd}
%\usepackage{tocloft}
%\usepackage{tocbasic}
%\usepackage[subnum]{cases}
\usepackage{imakeidx}
\makeindex
\usepackage[nottoc]{tocbibind}
%\numberwithin{equation}{section}
%\usepackage{makeidx} 
%\usepackage{fancyhdr,multirow,lscape,chngpage,calligra,float}
\usepackage[round]{natbib}
\counterwithin{equation}{chapter}
%\usepackage{titletoc}
%\usepackage{watermark}
%\usepackage[nottoc]{tocbibind}
%\usepackage{afterpage}
%\usepackage[T1]{fontenc}
%\setcounter{tocdepth}{1}
%\usepackage{indentfirst}
%\usepackage{multirow,lscape,chngpage,calligra,float}
%\usepackage[authoryear]{natbib}
%\usepackage[utf8]{inputenc}
%\newtheorem{thm}{Theorem}[section]
%\newtheorem{dfn}[thm]{Definition}
%\newtheorem{rem}[thm]{Remark}
%newtheorem{ex}[thm]{Example}
%\newtheorem{remex}[thm]{Remarks and Examples}
%\newtheorem{pro}[thm]{Proposition}
%\newtheorem{cor}[thm]{Corollary}
%\newtheorem{lem}[thm]{Lemma}
%\newtheorem{no}[thm]{Note}
%\newtheorem{ope}[thm]{Open Problem}
%\newtheorem{que}[thm]{Question}
%\newenvironment{proof}[1][Proof] {\begin{trivialist}
%\item[\hskip \labelsep {\bfseries #1}] } {\end{trivialist}}
\makeindex
%\setcitestyle{square}
\def\tableshortname{Table}
\def\figureshortname{Figure}
%\def\bibname{Bibliography}
%\includeonly{titlepage}
\linespread{1.5}
\begin{document}
%
%\newpage
%\include{Symbols}
%\include{Abstract}
%\include{Publication}
%\include{References}
%\include{presentations}
\newpage
\include{title}
\newpage
\include{Certificate}
\pagenumbering{roman}
\newpage
\include{Acknowledgments}
\pagenumbering{arabic}
\newpage
\tableofcontents
\mainmatter 
\include{Symbols}
\include{Introduction}
\include{Chapter2}
\include{Chapter3}
\include{Chapter4}
\include{Chapter5}
\include{Chapter6}

%   \include{Chapter7}
%   \include{conclusion}

    \include{References}
    \printindex
\include{Publication}
\end{document}