About the flag into Language switcher module, you need to make sure that you have all steps below
1) The Content Language parameters in the Language Manager
2) Assigning these Content languages to various items using the “Language” parameter.
3) Create a correct site structure • Important !!!
4) Defining a Default Home page Menu item per language and keep one separate tagged to “All” languages.
5) The languagefilter System Plugin
6) The mod_languages Module (also called Langswitcher)
7) Define a default site template per Content language if needed.
8) Make sure the site language packs are installed and enabled for any content language you want to display