documentclass{article}
usepackage[tmargin=1.25in,bmargin=1.25in,lmargin=1.5in,rmargin=1.5in]{geometry}
usepackage{fancyhdr}

renewcommand{sfdefault}{phv} % Arial

begin{document}
fontfamily{ptm}selectfont
pagestyle{fancy}
renewcommand{headrulewidth}{0pt}

sffamily
noindentrule{14cm}{1pt}
begin{center}
huge{textbf{Title is using correct font}}
par
vspace{7mm}
end{center}
vspace{-baselineskip}
noindentrule{14cm}{1pt}
fontfamily{ptm}selectfont
begin{flushleft}

vspace{7mm}
par
renewcommand{sfdefault}{large{textbf{ABSTRACT should be arial 12}}}
sfdefault
par
fontfamily{ptm}selectfont
vspace{7mm}
par
Correctly using  Times New Roman 11
vspace{7mm}
par
renewcommand{sfdefault}{large{textbf{1 quad quad INTRODUCTION should be arial 12}}}
sfdefault
par
fontfamily{ptm}selectfont
vspace{7mm}
par
Correctly using  Times New Roman 11
vspace{7mm}
par

renewcommand{sfdefault}{large{textbf{2 quad quad METHODOLOGY should be arial 12}}}
sfdefault
par
fontfamily{ptm}selectfont
vspace{7mm}
par
Correctly using  Times New Roman 11
vspace{7mm}
par
pagestyle{fancy}

end{flushleft}
end{document}

documentclass[11pt]{article}
usepackage[vmargin=1.25in,hmargin=1.5in]{geometry}

usepackage{times}               % Times Roman
usepackage[scaled=0.86]{helvet} % Helvetica

usepackage{sectsty}
sectionfont{largesffamily}

begin{document}
raggedright

hrule
begin{center}
hugebfseriessffamily Title is using arial
end{center}
hrule

section*{ABSTRACT now uses arial}

Correctly using Times Roman

section{INTRODUCTION now uses arial}

Correctly using Times Roman

section{METHODOLOGY now uses arial}

Correctly using Times Roman
end{document}