The mozilla-firefox package you have installed is the esr ( Extended Support Release) edition which is the default.
There is also the mozilla-firefox-noesr edition which is as mozilla-firefox slackware package.
Installing the package removes the other. Same for the locales. mozilla-firefox-l10n-YOUR-LOCALE and mozilla-firefox-noesr-l10n-YOUR-LOCALE
Where YOUR-LOCALE is el or it or fr etc
There is also the latest google-chrome-50.0.2661.86 64 bit package and an old google-chrome-48.0.2564.109 for 32 bit since google-chrome only updates 64 bit architecture now.