You ask for many questions in the same question, which all of these answer are detailled on the handbook and in the example joined https://ctan.org/pkg/reledmac.
Here a MWE of facing page
\documentclass{article}
\usepackage{polyglossia,fontspec,xunicode}
\usepackage{libertineotf}
\setmainlanguage{english}
\usepackage[series={A},noend,noeledsec,noledgroup]{reledmac}
\usepackage{reledpar}
\begin{document}
\date{}
\title{Parallel}
\maketitle
\begin{abstract}
This file provides two minimal examples of typesetting parallel texts with reledmac plus reledpar.
The first minimal example is parallel typesetting in columns, the second one is parallel typesetting in pages.
\end{abstract}
\begin{pages}
\begin{Leftside}
\beginnumbering
\pstart
Left side paragraph. Left side paragraph. Left side paragraph. Left side paragraph. Left side paragraph. Left side paragraph. Left side paragraph. Left side paragraph.
\pend
\pstart
Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph. Other left side paragraph.
\pend
\endnumbering
\end{Leftside}
\begin{Rightside}
\beginnumbering
\pstart
Right side paragraph. Right side paragraph. Right side paragraph. Right side paragraph.
\pend
\pstart
Other right side paragraph. Other right side paragraph. Other right side paragraph. Other right side paragraph. Other right side paragraph. Other right side paragraph. Other right side paragraph.
\pend
\endnumbering
\end{Rightside}
\end{pages}
\Pages
\end{document}
If you want to restart lineation at each page, use
\lineation*{page}
To make a critical footnote, do
\edtext{lemma}{\Afootnote{text of the critical footnote}}
To make a familiar footnote, without lemma but with a footnotemark, do
text\footnoteA{texte of the footnote}
As you use familiar footnote on both side, you should do multiple run to get the correct number. In general, with reledmac/reledpar, it is better to use tools like latexmk wich automatically does multiple runs for you.
But, in general, it is also better to read the handbook…