Hi Anna,
1. You can't sync multiple GTW's to a single Marketo Program.
2. I haven't tried this
3. You could use Marketo segments on the language field of a lead. You can use segments for dynamic content in your Marketo assets. Let your international teams provide you the translations for it. This enables you to use a single Marketo Program and GTW session for all languages. However the GTW session it self is only in one language of course.
Our platform (BrightTALK) publishes recorded versions of webinars immediately after the live event concludes, so we typically just pick a time zone for the live event and send the on-demand link to everybody who missed it.
Since anybody viewing this thread is obviously interested in webinars, I'll re-post this comment of mine from another thread:
The presentations below contain tons of data on webinar trends and best practices. Some of the topics covered include: