SweepPress

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.

All Dev4Press free and lite plugins can be translated via WordPress.org and their translation services. Each plugin on WordPress.org has support for translation, and you can get to it through the plugin Developer panel. To translate plugins on WordPress.org, you need a WordPress.org account. But, if you want to handle translations on your own, each plugin has a POT file with the list of all translation strings

In general, yes. WordPress and most plugins will register the CRON jobs they need if they detect that job is not registered. There are, however, some plugins that register jobs on plugin activation, and they will not try to detect if the job is missing or not. But, most plugins will recreate missing jobs.