Beamer - maketitle two language

Question

I am trying to have a title page with the title be in English and the rest elements in Greek. I search and tried a lot but I can' get it work.

I tried \title{English title}, \title{{\lat English title}}, \title{{\selectlanguage{english} English title}}.

I removed babel but some characters are not being recognized.

I am using SublimeText 3 with LatexTools as builder and engine pdflatex.

I tried: this and this.

The error log is huge. I posted the the first few lines.

Argument of \bbl@pop@lang has an extra }. [\begin{document}]

Paragraph ended before \bbl@pop@lang was complete.

Paragraph ended before \HyPsd@@ProtectSpacesFi was complete.

LaTeX Error: Missing \begin{document}. [\begin{document}]

Extra }, or forgotten \endgroup. [\begin{document}]

Use of \HyPsd@RemoveMask doesn't match its definition. [\begin{document}]

Undefined control sequence. [\begin{document}]

Paragraph ended before \HyPsd@RemoveBraces was complete.

LaTeX Error: Missing \begin{document}. [\begin{document}]

Extra }, or forgotten \endgroup. [\begin{document}]

Argument of \HyPsd@CheckCatcodes has an extra }. [\begin{document}]

Paragraph ended before \HyPsd@CheckCatcodes was complete. [\begin{document}]

Paragraph ended before \HyPsd@RemoveMask was complete. [\begin{document}]

%\documentclass[notes]{beamer}
\documentclass[hide notes greek]{beamer}
%\documentclass[notes=only]{beamer}

\mode<presentation>
{
    \usetheme{Rochester}
}

%Packages

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,greek]{babel}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{csquotes}
\usepackage{fancyhdr}
\usepackage{listings}
\usepackage{color}
\usepackage{graphicx}
\usepackage{algpseudocode}
\usepackage{algorithm}
\usepackage{subcaption}
\usepackage{tikz}
\usepackage{tikz-qtree}
\usepackage{tree-dvips}
\usepackage{lmodern}% http://ctan.org/pkg/lm

\usetikzlibrary{calc,trees,arrows,decorations.pathmorphing,backgrounds,positioning,fit,matrix}

%Math Fonts

\usefonttheme[onlymath]{serif}
\setbeamertemplate{bibliography item}{\insertbiblabel}

\bibliography{references}

\newcommand{\lat}{\selectlanguage{english}}
\newcommand{\gre}{\selectlanguage{greek}}

\hypersetup{
    unicode=true
}

%Page Title Variables

\title{English title}
\subtitle{A greek subtitle}
\institute{A greek name institute}
\author{Greek name}
\subject{}
\date{}

\begin{document}
    \begin{frame}
        \titlepage
    \end{frame}
\end{document}

Answer 1

You could try with \foreignlanguage{english}{English title}

%\documentclass[notes]{beamer}
\documentclass[hide notes greek]{beamer}
%\documentclass[notes=only]{beamer}

\mode<presentation>
{
    \usetheme{Rochester}
}

%Packages

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english,greek]{babel}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{csquotes}
\usepackage{fancyhdr}
\usepackage{listings}
%\usepackage{color}
%\usepackage{graphicx}
\usepackage{algpseudocode}
\usepackage{algorithm}
\usepackage{subcaption}
\usepackage{tikz}
\usepackage{tikz-qtree}
\usepackage{tree-dvips}
\usepackage{lmodern}% http://ctan.org/pkg/lm

\usetikzlibrary{calc,trees,arrows,decorations.pathmorphing,backgrounds,positioning,fit,matrix}

%Math Fonts

\usefonttheme[onlymath]{serif}
\setbeamertemplate{bibliography item}{\insertbiblabel}

\bibliography{references}

\newcommand{\lat}{\selectlanguage{english}}
\newcommand{\gre}{\selectlanguage{greek}}

\hypersetup{
    unicode=true
}

%Page Title Variables

\title{\foreignlanguage{english}{English title}}
\subtitle{A greek subtitle}
\institute{A greek name institute}
\author{Greek name}
\subject{}
\date{}

\begin{document}
    \begin{frame}
        \titlepage
    \end{frame}
\end{document}

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Off topic: No need for \usepackage{color} and \usepackage{graphicx}, beamer already provides these functionalities.