Essentially, you can't really force these skills on kids. These things happen on individual pace for every kid out there. Some are better at art, some are better at speech, some are better at math and some learn to read earlier than others. That's why the school starts when it starts. By that time development seems to even out across the board.

No, it is not expected. The part of brain responsible for reading can develop any time between 4 and 7 years old. Most are there by 6 and plenty of 5 years old are not there yet.

By the time they are 8, there is no difference between former early readers and other kids, so there is no reason to worry about it.