Yes, all players and coaches wear the uniform number of 42 on Jackie Robinson Day.
Yes, they are required to wear hats. It is a part of the required uniform for all baseball players.
It is the clothing that the players wear.
All of them.
No. Players didn't wear uniform numbers back then
The Houston Astros have had 35 different players wear uniform number 22. Currently, Carlos Corporan wears this number. Uniform number 22 was first worn by Al Heist in 1962.