Newbie: Whats the Best Practice to install multiple emacs and hand-install packages

Newbie: Whats the Best Practice to install multiple emacs and hand-install packages

[gnuist]

[Context]
These days, you frequently need more than one version of emacs on a machine.

An older version that you are used to and then transitioning to a newer version where things have been so drastically reorganized that you need to customize it to your liking or muscle memory of the previous one or making the decision to gradually accept new changes.

Assuming a relay emacs file that some newbies won't know, you can write where the executable is and then send it to where the second .emacs is and .emacs.d is where you have elpa, melpa and gnu subdirectores.

[Question] What is the Best Practice/Best Location to put the hand installed packages so they do not interfere with the existing ones using package manager. Also, at some time, those might appear as packages. Also, how to include them in the path of emacs, different from path in linux or windows or mac OSes. 

Also, is there a command inside emacs so that I just say, find-file and using its internal path reach, it gives me the list of files with that name that it can reach without opening them? As you can see, I have two .emacs file, first one is relay and the other is in tilde.

This question has arisen in the course of installing zones package where these 4 packages are needed:


https://www.emacswiki.org/emacs/Zones              ... zones package installed using package manager from repos
https://www.emacswiki.org/emacs/HighlightLibrary   ... ditto
https://www.emacswiki.org/emacs/IsearchPlus        ... does not exist in elpa/melpa and how to install by hand PROPERLY
https://www.emacswiki.org/emacs/facemenu+.el       ... does not exist in elpa/melpa and probably not needed