Compiling error regarding scrlayer-scrpage

Question

A solution for one of my questions works well for the one who provided it, but results in the error "Missing \begin{document}. \ofoot*{\pagemark" for me during compiling. Could it be a problem with my installation, packages, os? On this online latex compiler the same error is preventing him to produce an output so may I don´t have a problem but the code need to be changed?

\documentclass[12pt,a4paper,listof=flat,oneside]{scrartcl}
\KOMAoptions{captions=tableheading}
\usepackage{nicefrac}
\usepackage{scrlayer-scrpage}
\ihead{\headmark}
\chead*{}
\ofoot*{\pagemark}
\cfoot*{}
\pagestyle{scrheadings}
\automark[section]{section}
\setkomafont{pagehead}{\normalfont}
\KOMAoptions{
    captions=tableheading,
    headsepline=true,
    markcase=upper}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc} 
\usepackage{amssymb}
\usepackage{mathtools}
\usepackage{xfrac}
\usepackage{xspace}
\newcommand{\eg}{\mbox{e.\,g.}\xspace}
\newcommand{\Eg}{\mbox{E.\,g.}\xspace}
\usepackage[english]{babel} 
\usepackage[left=3.00cm, right=3.00cm, top=2.00cm, bottom=2.5cm, includeheadfoot]{geometry} 
\usepackage[onehalfspacing]{setspace} 
\usepackage{lmodern}
%\usepackage{helvet}
%\renewcommand{\familydefault}{\sfdefault} 
%\fontfamily{phv}\selectfont
\usepackage{color}
\usepackage[
  pdftoolbar = false,
  pdfmenubar = false, 
  pdftitle   = mwe,
  pdfauthor  = {author},
  colorlinks,
  allcolors =  {blue},
  bookmarks         = true,
  bookmarksopen     = true, 
  bookmarksnumbered = true
]{hyperref}
\usepackage{subcaption}


\begin{document}
\thispagestyle{plain.scrheadings}
\section{Chapter one} \label{sec:ChapterOne}
This text shows the current options that I have used for the printed version of my document. What and why would you change something? 
\begin{itemize}
\item Referencing in blue. \Eg: Chapter one on page \ref{sec:ChapterOne}
\item In-text math mode I use tfrac or nicefrac like this $\tfrac{1}{2}$ or this $\nicefrac{1}{2}$ and dfrac in the stand-alone equations. Or is sfrac of the xfrac package the way to go? $\sfrac{1}{2}$. What is the difference?
\item Different fonts for print-out and digital copy? \Eg helvet for pdf for no serifs?
\end{itemize}
\newpage
Thats what the pagestyle I have choosed looks like, but there is a warning about fancyhdr, how to produce the same output with KOMA?

\begin{figure}[!htbp]
    \null\hfill
    \begin{minipage}[b]{0.4\linewidth}
    \centering \includegraphics[width=\textwidth]{example-image-a}
    \subcaption{Example A}\label{fig:a}
    \end{minipage}
    \hfill
    \begin{minipage}[b]{0.4\linewidth}
    \centering \includegraphics[width=\textwidth]{example-image-b}
    \subcaption{Example B}\label{fig:b}
    \end{minipage}   
    \hfill\null   
\caption{Two figures with subcaption and minipage}
\end{figure}    
\end{document}

Answer 1

The mentioned online compiler uses a really old KOMA-Script version:

Document Class: scrartcl 2013/12/19 v3.12 KOMA-Script document class (article)

Current version is 3.22 and version 3.23 will be soon available on CTAN. The starred versions of \ihead etc. are introduced in version 3.14.

If you can not update, then use:

\usepackage[automark,markcase=upper,headsepline]{scrlayer-scrpage}
\clearpairofpagestyles
\ihead{\headmark}
\ofoot[\pagemark]{\pagemark}

Complette example:

\documentclass{scrartcl}
\usepackage[automark,headsepline,markcase=upper]{scrlayer-scrpage}
\clearpairofpagestyles
\ihead{\headmark}
\ofoot[\pagemark]{\pagemark}

\usepackage{blindtext}
\begin{document}
\thispagestyle{plain}
{\huge\KOMAScriptVersion\par}
\blinddocument
\end{document}

Output by the Online Compiler mentioned in the question:

Answer 2

The posted code gives

! Paragraph ended before \@fileswith@ptions was complete.

because of the blank line in the hyperref options.

If you remove that

\usepackage[
  pdftoolbar = false,
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%<<<<<<<<<<,
  pdfmenubar = false, 
  pdftitle   = mwe,
  pdfauthor  = {author},
  colorlinks,
  allcolors =  {blue},
  bookmarks         = true,
  bookmarksopen     = true, 
  bookmarksnumbered = true
]{hyperref}

Then it gives the error

! Undefined control sequence.
<argument> \undefinedpagestyle 

l.48 \thispagestyle{leer}

I can not guess if that is a typo for a page style that is defined, or if the definition of that page style is missing. But if you remove that, so:

%\thispagestyle{leer}

then the document runs without error.