GD Knowledge Base

Yes. POT file is provided as a base for translation in the root folder for each plugin. Translation files should go into languages directory, and WordPress must be set to your language to load the file. As an alternative, translation file can go into wp-content/languages/plugins directory.

The file name for translated and compiled MO file must be the same as POT file with the addition of language code: {plugin-name}-{language-code}.mo.

You can check out this for translating plugins using POEdit program:
support.dev4press.com/kb/article/translating-plugins-or-themes-using-poedit

Yes. Each site in the network can activate and use the plugin.

Plugin is adding own styling for the features it adds, but there is no way to make styles completely immune to other stylesheets or styles added by other plugins or theme. Many themes are adding styles that are very aggressive and they can be made to have higher priority in styling certain elements. In that case, a theme can cause issues with the plugin features styling.

The only solution is to identify the styles that are causing problems and add new styles to fix that. This has to be done for every theme that causes problems.

Child themes provided with GD Knowledge Base Pro are not required. The plugin works with any theme, and child themes provided are examples to get you started with custom development in case you want to customise GD Knowledge Base Pro plugin templates. Using child themes is not recommended for non-developers.

If you want to add only styling changes, you can add your own custom CSS into your theme style.css file.

All Dev4Press plugins and addons require jQuery. But, they will work only if the jQuery is loaded with the WordPress proper Enqueue method. If you are replacing jQuery that comes with WordPress with some other version loaded from other location, my plugins will not function properly, and that goes the same for most of the other WordPress plugins that depend on the proper way for loading jQuery.