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Use several Emacs configurations/versions simultaneously

I want to use several emacs configurations/versions simultaneously so that no configuration disturbs each other, each with their own configuration directory and elpa repository. I heard about the trick with symlinking ~/.emacs.d and ~/.emacs, but that is not what I want, because it'd be best if I can run my default emacs installation and simultaneously a testing installation (new emacs releases) or another setup like Spacemacs or Prelude.

Is there any decent way to do this?