4) Most number of matches played between two teams
This record is up for the grabs. Brazil and Sweden; Argentina and Germany; Germany and Serbia. Each pair have played each other 7 times in the World Cup history with Argentina and Germany facing 3 of the 7 ties in the finals of the World Cup. Here the math gets critical as if Brazil tops the group and Sweden finish second, they will face each other in the Round of 16, and vice-versa of course. The same course will follow for Serbia and Germany, and they are likely to meet in the Round of 16 if both qualify.
The one with Argentina and Germany will see, winners of Round of 16 matches. Given Argentina wins their round and Germany emerges victorious in theirs, the pair will meet each other in the Quarter Finals of the World Cup. By the looks of it, one can expect the Germany vs. Argentina pair break the record.