JIT Emacs parallel world

[Emanuel Berg]

I think the easiest way to get my gear from
Emacs 24 to Emacs 27 JIT is to start over and
bring stuff over one piece at a time,
correcting each error/warning as I go along.

So the current situation is, I have Emacs 24
installed from the repos, I have Emacs-w3m
installed from the repos, I have all my gear in
a directory in ~/.emacs.d, which is loaded from
~/.emacs - all everyday stuff in other words.

Emacs 27 JIT tho I got from Git and built
manually - if that is the right word - but
I didn't install it. So I have it in
a directory all to itself.

Now, in order to carry out my plan, how can
I tell Emacs 27 JIT to look for another init
file (NOT the one I have for Emacs 24,
~/.emacs), and use another Emacs directory
(NOT ~/.emacs.d) ?

TIA

-- 
underground experts united
http://user.it.uu.se/~embe8573