Line numbers in tcolorbox, "notebook"/answer lines style

Question

I wanted to adapt the answer here to insert line numbers on the left side (inside the box) -- just like listings in the tcolorbox package.

I have also tried to put an optional number of lines argument in the newtcolorbox command, but as it didn't work, it ended up with the shoddy manual vspace instead.

\documentclass{article}
\usepackage[most]{tcolorbox}
\usepackage{lmodern}
\usepackage{blindtext}
\usepackage{calc}

\newtcolorbox{notebook}{
    enhanced,
    breakable,
    colback=green!10,
    colframe=green!65!black,
    left=.7in,
    underlay={%
        \begin{tcbclipinterior}
        %\shade[inner color=green!80!yellow,outer color=yellow!10!white]
%(interior.north west) circle (2cm);
        \draw[help lines, ystep=\baselineskip, xstep=\linewidth, 
            shift={(interior.north west)}](interior.south west) grid (interior.north east);
        \draw[help lines] ([xshift=.5in]interior.north west)--
            ([xshift=.5in]interior.south west);
        \end{tcbclipinterior}}
    }

\usepackage{lineno}


\begin{document}
\blindtext[1]
\begin{notebook}
\blindtext[3]
\end{notebook}

\begin{notebook}
\vspace{20\baselineskip}
\linenumbers
\end{notebook}


\end{document}

Answer 1

Probably I misunderstand your question, but you can just add an optional parameter that inserts the empty lines using before upper.

\documentclass{article}
\usepackage[most]{tcolorbox}
\usepackage{lmodern}
\usepackage{blindtext}
\usepackage{calc}

\newtcolorbox{notebook}[1][0]{
    enhanced,
    breakable,
    colback=green!10,
    colframe=green!65!black,
    left=.7in,
    underlay={%
        \begin{tcbclipinterior}
        %\shade[inner color=green!80!yellow,outer color=yellow!10!white]
%(interior.north west) circle (2cm);
        \draw[help lines, ystep=\baselineskip, xstep=\linewidth, 
            shift={(interior.north west)}](interior.south west) grid (interior.north east);
        \draw[help lines] ([xshift=.5in]interior.north west)--
            ([xshift=.5in]interior.south west);
        \end{tcbclipinterior}},
    before upper=\vspace{#1\baselineskip}   
    }

\usepackage{lineno}


\begin{document}
\blindtext[1]
\begin{notebook}
\blindtext[3]
\end{notebook}

\begin{notebook}[20]

\end{notebook}
\end{document}

ADDENDUM: As for your additional request: here is something along those lines (partly inspired by this question).

\documentclass{article}
\usepackage[most]{tcolorbox}
\usepackage{lmodern}
\usepackage{blindtext}
\usepackage{calc}

\newtcolorbox{notebook}[1][0]{
    enhanced,
    breakable,
    colback=green!10,
    colframe=green!65!black,
    left=.7in,
    underlay={%
        \begin{tcbclipinterior}
        %\shade[inner color=green!80!yellow,outer color=yellow!10!white]
%(interior.north west) circle (2cm);
        \draw[help lines, ystep=\baselineskip, xstep=\linewidth, 
            shift={(interior.north west)}](interior.south west) grid (interior.north east);
        \draw[help lines] ([xshift=.5in]interior.north west)--
            ([xshift=.5in]interior.south west);
        \end{tcbclipinterior}},
    before upper={\ifnum#1>0
    \begin{internallinenumbers}\setcounter{linenumber}{1}
    \foreach \X in {1,...,#1}
    {~\par}
    \end{internallinenumbers}
    \fi
    }}

\usepackage{lineno}


\begin{document}
\blindtext[1]
\begin{notebook}
\blindtext[3]
\end{notebook}

\begin{notebook}[20]
\end{notebook}

\begin{notebook}[20]
\end{notebook}

\end{document}