Post here all non technical related topics about Formula One. This includes race results, discussions, testing analysis etc. TV coverage and other personal questions should be in Off topic chat.
They were all so-called "two-heat races" (red-flagged halfway and restarted later) - Both French GPs due to weather condition while both San Marino GPs due to accidents (which involved Berger and Senna respectively). For the missing-from-list races I guess I need to mention some other two-heaters... According to what I remember 1987 Mexican GP was a two-heat race when race red-flagged after Warwick or Cheever dismantled his Arrows car; 1994 Japanese GP split into two when heavy rain flooded the track; that's pretty much all I can recall so far.
You are correct. In addition to the two heat they also used agreggate timing - they added the times from the first heat to the second one shaking the finishing order sometimes.
I have information for one more grand prix missing from the list, find it and ask a new question.
Well I have to admit I consulted Wiki-almighty-pedia this time (really didn't have any idea for the race!), and it turned out that it was chaotic 1982 Detroit GP, red-flagged on seventh lap. So far as I remember 2011 Canadian GP, alongside with likes of 2010 Korean GP and also 2014 Japanese GP, wasn't a two-heat race but merely "one race which is suspended (not stopped) halfway and get going afterwards". Quite interesting the practice of aggregation timing is not seen these days (which is good considering all the shuffle-ups of result after race).
