Disney has official opening and closing times. Let's say that the Magic Kingdom opens at 9:00 a.m. and closes at 9:00 p.m. You can arrive at the Magic Kingdom at 8:30 a.m. and, most times, you are allowed to enter the park and go all the way to the end of Main Street. There, you will find ropes marking off Adventureland, Liberty Square, the passageway through the castle to Fantasyland and Tomorrowland.
When 9:00 a.m. rolls around, the ropes are walked back by castmembers and when they reach the entranceway to each section of the park, the ropes are dropped. You are then allowed to ride any of the rides you want.
If you can arrive this early, this means that you are already through security, the turnstiles and are well into the park.
When the 9:00 p.m. closing time arrives, the park is officially closed but you are allowed to enter into any ride or attraction up until 8:59 p.m. So, you may be in a ride or attraction after closing time.
If you are staying at a Disney resort, you are allowed to enter into a designated park early or stay late. These are called Extra Magic Hours. These are posted on the Disney website.
If you arrive early at the parks (not extra magic hours), you can go to a certain point before the actual opening time. I have already told you about the Magic Kingdom. At MGM Studios, we were allowed to go all the way down the main street and to the large hat and the streets were sectioned off along the way. One time at the Animal Kingdom, we were allowed to go through the Oasis section but not allowed to cross the bridge. Another time, we were allowed to cross the bridge but not enter the other lands. At Epcot, you are allowed to go past the Leave a Legacy stones but not past Spaceship Earth.
We have always found it best to arrive early and get through security and the turnstiles before the mad rush. Never try to leave the parks at official closing time. The parks stay open after official opening times. Not the rides but the stores on the main drags are often open. Just sit back for a while and let the exodus of crowds thin out. Sometimes we are still in the park, sitting on a bench, eating ice cream 45 minutes to an hour after closing. That way, the transportation systems are not so overloaded.
If you have more questions, let me know. Lisa