The plugin 'Purify WordPress Menues' slims down the HTML output of WordPress menues to only the CSS classes and ID attributes you want.
Yes, it does.
Short answer: Normally not and if yes, you can take control of it.
Long answer: The default settings are to output only the CSS class for the current active menu item. If the theme's CSS uses also the other CSS classes and/or item ID attribute you will notice some undesirable visual effects on menues. In this case just find out which classes and/or IDs the theme uses and activate them via the plugin's options page until the effects disappear.
After activating the plugin deletes the id attributes an all CSS classes on every menue item except the CSS classes ".current-menu-item" in navigation menues and ".current_page_item" in page menues.
Your settings will be still stored in the WordPress database. After you re-activate the plugin all your settings are back.
Your settings will be deleted, too. In other words: There would not remain any useless settings of this plugin.
Yes. It does this way as default. You can activate the output of every menu item's id on the plugin's options page.
Normally, if you deselect every checkbox for page menues on the plugin's options page no class attribute should be there in page menues. But the WordPress files does not offer a gentle way to suppress the class attribute if it has no values. The plugin saves time and ressources by not trying an own way. If you would have a trick for deleting the empty class attibute with little effort please tell me about it.
Actually this languages are supported:
Further translations are welcome. If you have one please send me an email.
If you want to contribute a translation of the plugin in your language it would be great! You would find the *.pot file in the 'languages' directory of this plugin. If you would send the *.po file to me I would include it in the next release of the plugin.