Restart the numbering of the reference labels in the appendix body in overleaf

Question

I have created a supplementary section in my journal manuscript using the following script:

\appendix
%%%
\renewcommand{\appendixname}{S}
\renewcommand{\thesection}{S}
\renewcommand\thefigure{\thesection.\arabic{figure}}
\setcounter{figure}{0}
\renewcommand*{\thepage}{S\arabic{page}}
\setcounter{page}{1}
%%%
\begin{center}
\section*{Supplementary Material}
\end{center}
%%%
\subsection{Sub-heading1}

A separate bibliography also has been generated for the appendix using the multibib package as follows:

\usepackage[resetlabels]{multibib}
\newcites{supp}{Supplementary References}

and declaring

%% Loading supplementary bibliography style file
\bibliographystylesupp{unsrt}
% Loading supplementary bibliography database
\bibliographysupp{cas-sc-template-refs.bib}

\end{document}

resulting in a reference section that looks like this: Supplmentary References

However, the reference labels in the body text does not change:

S.2. Discussion
S.2.1. Subheading2
The role of the structural of squares and the circles is clearly seen in the interdependence of property on the values of energy and density as shown in Figures S.4a and S.4b. There is a clear clustering of data points based on the primary property as viewed against its dependence on secondary property in Figures S.4c. The high-value compositions are observed to be all apples and the medium value ones are observed to be oranges. The values thus predicted placed most of them in the low– and medium–value range [66].

The reference numbers are still from the main document's bibliography.

I have tried the \DeclareOption{resetlabels}{\continuouslabelsfalse} option in the multibib package documentation given in http://tug.ctan.org/tex-archive/macros/latex/contrib/multibib/multibib.pdf but to no avail.

Is there any way to renumber these reference labels as well?