1. If you use the full expression, then it's "masters of ceremonies". If you use the abbreviation, then it's MCs or emcees.
2. I'm sorry, but your sentence doesn't make any sense.
3. This is difficult to understand as well. What's the context? I think there's a misunderstanding of the verb "to support".
4. It's "are". The subject is "the Olympic Games", and "games" is in a plural form. You could simply check the sentence with an online search.
5. You need to learn passive and active voice. Simple as that. Again, your sentence is very unclear and there's another error with the verb.