Tony Conigliaro of the Red Sox with 24, all coming in 1964 at the age of 19.
104
There have been 255 Major League players that have hit for the Cycle in a game, there were 122 players in the American League that have accomplished the feat and 133 players in the National League that have accomplished the feat howevver the Miami Marlins and the San Diego Padres have not had any players hit for the Cycle.
In 2006, Jermaine Dye hit 44 home runs and Jim Thome hit 42.
zero
Delmon Young
As of the 2008 season, 97 players have hit a home run in their first MLB at bat. Click on the 'Players with a Home Run in Their First At Bat' link below to see a list of those players.
27
darryl strawberry and rusty staub
25 players
Since 1901, 94 players have homered before their "age 20 year" - which is their age on June 30. This may exclude a few players whose birthdays come before June 30 and homered before their birthday on that year, and vice versa, but the number should be about right.
Miguel Cabrera
104
65
2 players hit 40 or more home runs in 2008, both from the National League. R. Howard(47), and A. Dunn (40)
Joseph rivera
25
As many as the players can hit. There is no limit.