How can I add "Available at:" for my DOI and should I use @online or @article for citing

Question

I want the output as below:

(1) An online journal article with a DOI

(2) A website

(3) A journal article

I want to do a citing for An online journal article with a DOI using the format below:

My Output is:

I am using:

% An online journal article with a DOI using @article
@article{Test2,
    author = {Kovalchuk, Y. and Stewart, R. and Broadbent, M. and Hubbard, T. J. P. and Dobson, R. J. B.},
    title  = {Analysis of diagnoses extracted from electronic health records in a large mental health case register},
    journal = {Plus One},
    volume = "12",
    number = "2",
    date   = {2017},
    DOI = "http://dx.doi.org/10.1371/journal.pone.0171526",
}

If I use @online.

% An online journal article with a DOI using @Online
@online{Test1,
    author = {Kovalchuk, Y. and Stewart, R. and Broadbent, M. and Hubbard, T. J. P. and Dobson, R. J. B.},
    title  = {Analysis of diagnoses extracted from electronic health records in a large mental health case register},
    journal = {Plus One},
    volume = "12",
    number = "2",
    date   = {2017},
    url    = {http://dx.doi.org/10.1371/journal.pone.0171526},
}

The output below where the title become italic which I do not want for citing a website.

My Full MWE:

\documentclass{article}
\usepackage{xpatch}
% \usepackage[style = authoryear-comp, maxnames = 99]{biblatex}

\usepackage[backend=biber, 
% style=authoryear, 
 style=authoryear-comp,
% citestyle=authoryear, 
dashed=false,
maxcitenames=2,
maxbibnames=99,
giveninits,
alldates=comp,
dateabbrev=false,
uniquename=init]{biblatex}

% to make volume (number), eg. 4(2)
\newcommand*{\volnumdelim}{}
\DeclareFieldFormat[article,periodical]{number}{\mkbibparens{#1}}

\renewbibmacro*{volume+number+eid}{%
  \printfield{volume}%
  \setunit*{\volnumdelim}%
  \printfield{number}%
  \setunit{\addcomma\space}%
  \printfield{eid}}

\newcommand*{\jourvoldelim}{\addcomma\space}
\newcommand*{\jourserdelim}{\newunitpunct}
\newcommand*{\servoldelim}{\jourvoldelim}
\newcommand*{\volnumdatedelim}{\addspace}

\renewbibmacro*{journal+issuetitle}{%
  \usebibmacro{journal}%
  \setunit*{\jourvoldelim}%
  \iffieldundef{series}
    {}
    {\setunit*{\jourserdelim}%
     \printfield{series}%
     \setunit{\servoldelim}}%
  \usebibmacro{volume+number+eid}%
  \setunit{\volnumdatedelim}%
  \usebibmacro{issue+date}%
  \setunit{\addcolon\space}%
  \usebibmacro{issue}%
  \newunit}  
% to make volume (number), eg. 4(2)
\DeclareNameAlias{sortname}{family-given} %for second and third author name
\DeclareFieldFormat{postnote}{\printtext[bibhyperref]{#1}}

\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage[english]{babel}
\usepackage{csquotes}



\addto\captionsenglish{
\renewcommand{\listfigurename}{\textsf{List of Figures}}
\renewcommand{\listtablename}{\textsf{List of Tables}}
}

% Flag for whether to add front matter to TOC
\newtoggle{fulltoc}
\toggletrue{fulltoc}  % Change to \togglefalse{fulltoc} to remove front matter
\renewcommand{\contentsname}{Table of Contents}


\usepackage[unicode,colorlinks,citecolor=blue]{hyperref}


% for a chapter edited by a book
\usepackage{xpatch}
% \renewcommand*{\finalnamedelim}{\addspace\&\space} 
% \renewcommand*{\intitlepunct}{\space} (to become In:)
\renewcommand{\labelnamepunct}{\space} %to delete . after (1997)
% \DeclareFieldFormat[article, incollection, unpublished]{pages}{#1} % to add in PP. (page)
\DeclareFieldFormat[article, incollection, unpublished]{title}{#1}
% \renewcommand{\bibpagespunct}{\ifentrytype{article}{\addcolon}{\addperiod\addspace}} %cancel out this in order to add in PP. (page)


% for title italic
% \DeclareFieldFormat*{title}{\mkbibemph{#1}} %for title italic in all format (conference, paper..)
\DeclareFieldFormat*{title}{#1} %for conference title delete ".."
\DeclareFieldFormat[incollection]{title}{\mkbibemph{#1}} %for incollecion title italic ONLY
\DeclareFieldFormat[thesis]{title}{\mkbibemph{#1}} %for phdthesis title italic ONLY
% for title italic

% to delete "In:" for article
\renewbibmacro{in:}{%
  \ifentrytype{article}{}{\printtext{\bibstring{in}\intitlepunct}}}
% to delete "In:" for article


% for delete comma after Author A and Aurhor b
\DefineBibliographyExtras{english}{%
   \let\finalandcomma\empty
   \let\finalandsemicolon\empty
 }
\renewcommand{\compcitedelim}{\space\&\space}
\DeclareNameAlias{editorin}{given-family}

\newbibmacro*{byeditor:in}{%
  \ifnameundef{editor}
    {}
    {\printnames[editorin]{editor}%
     \setunit{\addcomma\space}%
     \usebibmacro{editorstrg}%
     \clearname{editor}}}     


\DeclareDelimFormat[textcite]{postnotedelim}{\addcolon\space}
\DeclareDelimFormat[parencite]{postnotedelim}{\addcolon\space}

% \DeclareFieldFormat{postnote}{#1}
\DeclareFieldFormat{postnote}{\printtext[bibhyperref]{#1}}
\DeclareFieldFormat{multipostnote}{#1}


% for references 's studies (year)
\renewcommand*{\nameyeardelim}{\addcomma\space}
\newcommand{\mycite}[1]{\citeauthor{#1}'s \citeyear{#1}}

\DeclareCiteCommand{\citeauthor}
  {\boolfalse{citetracker}%
   \boolfalse{pagetracker}%
   \usebibmacro{prenote}}
  {\ifciteindex
     {\indexnames{labelname}}
     {}%
   \printtext[bibhyperref]{\printnames{labelname}}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\citeyear} % <======================================
    {}
    {(\bibhyperref{\printdate})}
    {\multicitedelim}
    {}

\DeclareCiteCommand{\parencite}[\mkbibparens]
  {\renewcommand*{\postnotedelim}{\addcolon\space}%
   \usebibmacro{cite:init}%
   \usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \printtext[bibhyperref]{\usebibmacro{cite}}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

\DeclareCiteCommand{\cbx@textcite}
  {\renewcommand*{\postnotedelim}{\addsemicolon\space}%
   \usebibmacro{cite:init}}
  {\usebibmacro{citeindex}%
   \usebibmacro{textcite}}
  {}
  {\usebibmacro{textcite:postnote}}  



\makeatletter
\let\abx@macro@textciteOrig\abx@macro@textcite
\renewbibmacro{textcite}{% <============================================
   \bibhyperref{%
   \let\bibhyperref\relax\relax%
   \abx@macro@textciteOrig%
   }%
}%
\makeatother
% for references 's studies (year)





\DeclareFieldFormat{url}{Available at\addcolon\space\url{#1}}
\DeclareFieldFormat{urldate}{\mkbibbrackets{\bibstring{urlseen}\space#1}}
\DeclareFieldFormat[online]{title}{\mkbibemph{#1}}
\DefineBibliographyStrings{english}{%
  urlseen = {Accessed},
}

\DefineBibliographyExtras{english}{%
  \protected\def\mkdaterangecomp{%
    \mkdaterangetrunc{long}}%
  \protected\def\mkdaterangeterse{%
    \mkdaterangetrunc{short}}%
  \protected\def\mkdaterangecompextra{%
    \mkdaterangetruncextra{long}}%
  \protected\def\mkdaterangeterseextra{%
    \mkdaterangetruncextra{short}}%
  \protected\def\mkbibdatelong#1#2#3{%
    \iffieldundef{#3}
      {}
      {\thefield{#3}%
       \iffieldundef{#2}{}{\nobreakspace}}%
    \iffieldundef{#2}
      {}
      {\mkbibmonth{\thefield{#2}}%
       \iffieldundef{#1}{}{\space}}%
    \iffieldbibstring{#1}
      {\bibstring{\thefield{#1}}}
      {\dateeraprintpre{#1}\stripzeros{\thefield{#1}}}}%
}





\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}


% An online journal article with a DOI using @Online
@online{Test1,
    author = {Kovalchuk, Y. and Stewart, R. and Broadbent, M. and Hubbard, T. J. P. and Dobson, R. J. B.},
    title  = {Analysis of diagnoses extracted from electronic health records in a large mental health case register},
    journal = {Plus One},
    volume = "12",
    number = "2",
    date   = {2017},
    url    = {http://dx.doi.org/10.1371/journal.pone.0171526},
}

% An online journal article with a DOI using @article
@article{Test2,
    author = {Kovalchuk, Y. and Stewart, R. and Broadbent, M. and Hubbard, T. J. P. and Dobson, R. J. B.},
    title  = {Analysis of diagnoses extracted from electronic health records in a large mental health case register},
    journal = {Plus One},
    volume = "12",
    number = "2",
    date   = {2017},
    DOI = "http://dx.doi.org/10.1371/journal.pone.0171526",
}

%M Maintain this format Website
@online{Maintain1,
    author = {World Health Organization},
    title  = {Global Health Observatory Data Repository},
    date   = {2014},
    url    = {http://www.who.int/gho/database/en/},
    urldate = {2014-12-23},
}

% Maintaine this format for Journal
@article{Maintain2,
  title={The building information modelling trajectory in facilities management: a review},
  author={Parn, E. A. and Edwards, D. J. and Sing, M. C. P.},
  journal={Automation in Construction},
  volume={75},
  pages={45--55},
  year={2017},
}

\end{filecontents*}

\addbibresource{\jobname.bib}

\begin{document}
\nocite{WinNT}

This is a ABC done by \textcite{Test1}.
book \parencite{Test2}
\textcite{Maintain1}
\textcite{Maintain2}

\printbibliography
\end{document}

where output:

Thanks.

Answer 1

This question was already answered here: How to change "url" to "Available at" for citing a website in BibLatex?

I could change the DOI format by using the same process:

\DeclareFieldFormat{doi}{Available at\addcolon\space\url{#1}}

For the "no italic" part, I was inspired by the question described here: How to put & symbol in reference as paper title. I tried \& and the previous post. You need to redefine so that biblatex does not emphasize the text:

\DeclareFieldFormat[online]{title}{#1}

Final result:

EDIT

Alternative proposed by @moewe in the comments:

\DeclareFieldFormat{doi}{\bibstring{urlfrom}\addcolon\space\url{#1}}

This way you use a unique string for all formats that you would like to redefine. If you want to modify that string:

\DefineBibliographyStrings{english}{%
    urlfrom = {Available at}
}

To get all articles with italic titles you can use your previous commands:

\DeclareFieldFormat[article]{title}{\mkbibemph{#1}}

Last but not least, the "World Health Organization" has no family name. It is like a corporation so you must tell bib(la)tex to not parse the name. It's done by putting an additional pair of { }, like this:

author = {{World Health Organization}},