How to create custom table environment with a possibility to merge cells

I'm trying to create a custom table environment that has the following properties:

• It may be very long (i.e., longer than a page) and so I need to use a longtable
• It may (or may not) have long row.

I'm having problems on the long row, this is what I got:

I'm understanding where I'm wrong. \multirow sets a piece of text in a tabular or similar environment, spanning multiple rows. If rows are smaller than a piece of text, we having this problem:

 \documentclass[a4paper,14pt]{extarticle} \usepackage{amsmath} \usepackage{mathtext} \usepackage[T2A]{fontenc} \usepackage[russian]{babel} \usepackage{g0019} \usepackage{supertabular} \usepackage{graphics} \usepackage{float} \usepackage{caption} \usepackage{multirow} \usepackage{makecell} \input{glyphtounicode} \pdfgentounicode=1 \usepackage{pdflscape} \usepackage{gensymb} \usepackage{longtable} \usepackage[normalem]{ulem} \usepackage{moresections} \usepackage{textcomp} \usepackage{array} \usepackage{rotating} \usepackage{ifthen} \usepackage{anyfontsize} \usepackage{ragged2e} \usepackage{indentfirst} \usepackage{setspace} %% Captions setup \DeclareCaptionLabelFormat{gosttable}{Table #2} \DeclareCaptionLabelFormat{continued}{Continued table #2} \DeclareCaptionLabelSeparator{gost}{~---~} \captionsetup{labelsep=gost} \captionsetup[table]{labelformat=gosttable, margin={6ex,0pt}, indention=-5ex} \begin{document} \renewcommand\theadfont{\normalsize\scshape} \begin{landscape} \begin{longtable}[c]{|p{0.145455\linewidth}|p{0.381818\linewidth}|p{0.145455\linewidth}|p{0.145455\linewidth}|} \caption{Tabel 1} \label{tab:Tabel1} \\ \hline \thead[c]{\parbox{0.145455\textwidth}{\textbf{Purpose} }} & \thead[c]{\parbox{0.381818\textwidth}{\textbf{Description} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{Where is reflected} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{The way to achieve} }}\\ \hline \endfirsthead \captionsetup{labelformat=continued}\caption{} \\ \hline \thead[c]{\parbox{0.145455\textwidth}{\textbf{Цель} }} & \thead[c]{\parbox{0.381818\textwidth}{\textbf{Description} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{Where is reflected} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{The way to achieve} }}\\ \hline \endhead Consider additional questions & If necessary, consider additional aspects of development, such as the use of previously developed software, attestation of tools & Software Transfer Plan & Reflect decisions taken in the plans \\ \hline \multirow[lt]{3}{*}{\begin{minipage}{\linewidth}Identify software development standards \vspace*{0pt} \end{minipage}} & \multirow[lt]{3}{*}{\begin{minipage}{\linewidth}Identify development standards that will provide security requirements for the system in terms of the software being developed \vspace*{0pt} \end{minipage}} & Standards for the development of software requirements & \multirow[lt]{3}{*}{\begin{minipage}{\linewidth}Three standards have been developed \vspace*{0pt} \end{minipage}}\\* \cline{3-3} & & Standards for the software design process & \\* \cline{3-3} & & Standards for software encoding & \\ \hline \multirow[lt]{2}{*}{\begin{minipage}{\linewidth}Coordination of software development plans \vspace*{0pt} \end{minipage}} & \multirow[lt]{2}{*}{\begin{minipage}{\linewidth} Coordinate the development and modification of software plans. The results of the software planning process are monitored to ensure that the software plans and software development standards meet the requirements of this standard and ensure the coherent implementation of the software lifecycle processes \vspace*{0pt} \end{minipage}} & Software Quality Assurance Protocols & \multirow[lt]{2}{*}{\begin{minipage}{\linewidth} Report the verification results in the Verification Report \vspace*{0pt} \end{minipage}}\\* \cline{3-3} & & Results of software verification & \\ \hline \end{longtable} \end{landscape} \end{document} 

I have tried use table in table and this method is suitable for this table,

 \documentclass[a4paper,14pt]{extarticle} \usepackage{amsmath} \usepackage{mathtext} \usepackage[T2A]{fontenc} \usepackage[russian]{babel} \usepackage{g0019} \usepackage{supertabular} \usepackage{graphics} \usepackage{float} \usepackage{caption} \usepackage{multirow} \usepackage{makecell} \input{glyphtounicode} \pdfgentounicode=1 \usepackage{pdflscape} \usepackage{gensymb} \usepackage{longtable} \usepackage[normalem]{ulem} \usepackage{moresections} \usepackage{textcomp} \usepackage{array} \usepackage{rotating} \usepackage{ifthen} \usepackage{anyfontsize} \usepackage{ragged2e} \usepackage{indentfirst} \usepackage{setspace} %% Captions setup \DeclareCaptionLabelFormat{gosttable}{Table #2} \DeclareCaptionLabelFormat{continued}{Continued table #2} \DeclareCaptionLabelSeparator{gost}{~---~} \captionsetup{labelsep=gost} \captionsetup[table]{labelformat=gosttable, margin={6ex,0pt}, indention=-5ex} \begin{document} \renewcommand\theadfont{\normalsize\scshape} \begin{landscape} \begin{longtable}[c]{|p{0.145455\linewidth}|p{0.381818\linewidth}|p{0.145455\linewidth}|p{0.145455\linewidth}|} \caption{Процесс планирования ПО} \label{tab:ПроцесспланированияПО} \\ \hline \thead[c]{\parbox{0.145455\textwidth}{\textbf{Purpose} }} & \thead[c]{\parbox{0.381818\textwidth}{\textbf{Description} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{Where is reflected} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{The way to achieve} }}\\ \hline \endfirsthead \captionsetup{labelformat=continued}\caption{} \\ \hline \thead[c]{\parbox{0.145455\textwidth}{\textbf{Цель} }} & \thead[c]{\parbox{0.381818\textwidth}{\textbf{Description} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{Where is reflected} }} & \thead[c]{\parbox{0.145455\textwidth}{\textbf{The way to achieve} }}\\ \hline \endhead Consider additional questions & If necessary, consider additional aspects of development, such as the use of previously developed software, attestation of tools & Software Transfer Plan & Reflect decisions taken in the plans \\ \hline {\begin{minipage}{\linewidth}Identify software development standards \vspace*{0pt} \end{minipage} & {\begin{minipage}{\linewidth}dentify development standards that will provide security requirements for the system in terms of the software being developed \vspace*{0pt} \end{minipage} & \begin{minipage}{\linewidth} \begin{tabular}{p{\textwidth}@{\hskip 0cm}} Standards for the development of software requirements \\ \hline Standards for the software design process \\ \hline Standards for software encoding \end{tabular} \end{minipage} & {\begin{minipage}{\linewidth}Three standards have been developed \vspace*{0pt} \end{minipage} \\ \hline {\begin{minipage}{\linewidth}Coordination of software development plans \vspace*{0pt} \end{minipage} & {\begin{minipage}{\linewidth}Coordinate the development and modification of software plans. The results of the software planning process are monitored to ensure that the software plans and software development standards meet the requirements of this standard and ensure the coherent implementation of the software lifecycle processe \vspace*{0pt} \end{minipage} & \begin{minipage}{\linewidth} \begin{tabular}{p{\textwidth}@{\hskip 0cm}} Software Quality Assurance Protocols \\ \hline Results of software verification \end{tabular} \end{minipage} & {\begin{minipage}{\linewidth}Report the verification results in the Verification Report \vspace*{0pt} \end{minipage} \ \hline \end{longtable} \end{document} 

but the document has tables of a different kind for which it does not fit. For example:

 \documentclass[a4paper,14pt]{extarticle} \usepackage{amsmath} \usepackage{mathtext} \usepackage[T2A]{fontenc} \usepackage[russian]{babel} \usepackage{g0019} \usepackage{supertabular} \usepackage{graphics} \usepackage{float} \usepackage{caption} \usepackage{multirow} \usepackage{makecell} \input{glyphtounicode} \pdfgentounicode=1 \usepackage{pdflscape} \usepackage{gensymb} \usepackage{longtable} \usepackage[normalem]{ulem} \usepackage{moresections} \usepackage{textcomp} \usepackage{array} \usepackage{rotating} \usepackage{ifthen} \usepackage{anyfontsize} \usepackage{ragged2e} \usepackage{indentfirst} \usepackage{setspace} %% Captions setup \DeclareCaptionLabelFormat{gosttable}{Table #2} \DeclareCaptionLabelFormat{continued}{Continued table #2} \DeclareCaptionLabelSeparator{gost}{~---~} \captionsetup{labelsep=gost} \captionsetup[table]{labelformat=gosttable, margin={6ex,0pt}, indention=-5ex} \begin{document} \renewcommand\theadfont{\normalsize\scshape} \begin{longtable}[c]{|p{0.300000\linewidth}|@{}p{0.300000\linewidth}|@{}p{0.300000\linewidth}|} \caption{table 2} \label{tab:table2} \\ \hline \multicolumn{2}{|c|}{\thead{\textbf{Options} }} & \multirowthead{2}{\parbox{0.300000\textwidth}{\centering \textbf{The project to develop on-board software} }}\\* \cline{1-2} \thead[c]{\parbox{0.300000\textwidth}{\textbf{Area} }} & \thead[c]{\parbox{0.300000\textwidth}{\textbf{Field name} }} & \\ \hline \endfirsthead \captionsetup{labelformat=continued}\caption{} \\ \hline \multicolumn{2}{|c|}{\thead{\textbf{Options} }} & \multirowthead{2}{\parbox{0.300000\textwidth}{\centering \textbf{The project to develop on-board software} }}\\* \cline{1-2} \thead[c]{\parbox{0.300000\textwidth}{\textbf{Area} }} & \thead[c]{\parbox{0.300000\textwidth}{\textbf{Field name} }} & \\ \hline \endhead \begin{minipage}{\linewidth}Information \vspace*{0pt} \end{minipage}& \begin{minipage}{\linewidth} \begin{tabular}{p{\textwidth}@{\hskip 0cm}} Description \\ \hline Object's Unique identificator \\ \hline Home page \\ \hline Public \\ \hline Parent project \\ \hline Inherit participants \end{tabular} \end{minipage} \hline \end{longtable} \end{document} 

What can I do?