This is an old revision of the document!
Prevent Firefox from starting automatically - https://support.mozilla.org/en-US/kb/firefox-starts-automatically-when-i-restart-window
https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles http://kb.mozillazine.org/Shortcut_to_a_specific_profile
about:profiles
https://support.mozilla.org/en-US/products/firefox/sync-and-save
https://support.mozilla.org/en-US/kb/send-tab-firefox-desktop-other-devices