Samsung Galaxy S II :: Contacts And Voice Recognition Settings?

The following questions are probably more Android-related in general, and not SGSII - specific. But as the SGSII is my first Android smartphone, please bear it with me and try to explain everything in layman's terms 1. In Contacts, what exactly does the "Merge with Google" option do (apart from displaying that little "g" icon next to a contact)? Also, after using it, I don't see to be able to revert the action - is it still possible?. Is it only possible to synchronize my Contacts with my Google account after the above mentioned "Merge with Google" action has been applied, or are they completely separate? E.g. if I add a new contact to my Phone, will it get synchronized with Google even if I don't Merge it with Google first?

3. Is it possible to also synchronize other contacts (like those from Facebook, LinkedIn, etc) in order to store them on my Google account for safety reasons4. Does the Google contacts synchronization work also the other direction, i.e. after I edit My Contacts on my Google accont, can I just use "Synchronize" in the SGSII to update the Phone contacts? Or do I need to delete all Contacts from my Phone first, and only then synchronize to the current Google version?5. I write messages/emails in English as often as I do in Polish. When I set Polish as the input language in Voice Recognition settings, and happen to compose a message in English using voice recognition, it often happens some Polish words are generated (and vice versa). I thought it would be logical if - apart from the global input language setting - the keyboard input language settings (changeable via the Space bar) - would eliminate the problem (ie. the VR engine should expect and use only English words when the keyboard is set to Eng, and so on) - but it doesn't seem to work.