To answer your first question, number 42 is being worn on every jersey to honor Jackie Robinson.
The entirety of the United States, apart from those games unfortunate enough to be called off due to the elements, are all wearing a number 42 jersey in respect of Jackie Robinson, a baseball hall of famer.
In fact you won't find the number 42 jersey anywhere in Major League Baseball as every single team retired it in a league wide initiative back in 1997.
The reason this is all happening is because Jackie Robinson was the first person to break the color barrier in Major League Baseball 50 years ago today.
On April 15 1947, the Brooklyn Dodgers as they were then were the first team to start an African-American player. This ended the segregation of black players into their own separate league (the Negro League) and Robinson was the champion of this change.
His achievements however are not singles to race but to performance as well. 1947 rookie of the year, 1949 league MVP and 1962 inductee into the hall of fame, Robinson's career spoke of his achievements as his legacy, not his heritage.
That was something he was very keen to establish for all his plaudits that his performances should be what was remembered, not his colour. It was for that reason alone he accepted his hall of fame entrance.
But it cannot be ignored that Robinson flew in the face of convention, breaking the colour barrier nearly four years before the Army was desegregated by then president Harry Truman, seven years before the segregation of schools was ruled unconstitutional. It was even eighteen years before the Civil Rights act was passed and Robinson was entered into the hall of fame a full year before Martin Luther King Jr delivered his "I have a dream" speech to the masses.
Since 2004, the league has recognized the achievements, the legacy and the importance of Robinson, who passed away in 1972. Every April 15 for the past ten years, Jackie Robinson day has been celebrated by the league.
This annual celebration brings to light the diversity that the country, through sport, has tried to achieve over the 20th and 21st century. It's interesting to note that there are currently 62 active African-American players in the MLB in 2014.
In a time where athletes, regardless of colour are opting for quicker athletic success and the glamour that comes with football and basketball, it should not be forgotten that the first steps were made on the diamond and that, given the size of the league, more diversity in the home nation should be strived for and achieved.