Star Spangled Banner and O Canada were the only two played.  If they were going to play an anthem for everyone there, it would have ran for an hour or more. 

I've never seen them play multiples during opening before,  but then I have not seen a lot of opening ceremonies televised.  I would have expected either nothing, or O Canada at the opening ceremony since it was in Toronto.   

Usually at the podium ceremony they play the winning driver and the winning team's anthem.  If they are the same, they only play it once...for years  thousands of people probably thought Das Deutschlandlied and Fratelli d'Italia were all one song from hearing them together after every race when Schumacher won.  lol  

It is interesting to see how differently different coutries citizens react to their anthems...some are very somber, some are very joyous.  I suppose it is partly a difference in national cultures.

I brought this up in response to the massive fuss thrown a few weeks ago because the Mexican anthem was played at an event between the US and Mexico.  I fail to see the difference.