There is a bus that will take you to other parks yes
The only way would be a bus. But if you are going from EPCOT to there, then the Skyliner is an option.
Yes there is a direct bus from Animal Kingdom to Hollywood Studios. Be aware there is also an Animal Kingdom Lodge which is a hotel, so be sure to read the bus directory to find the correct queue.
Some parks you can take the boats to different parks others the monorail and others you will need to go to Disney Springs to get a bus to a different park. But as most know if you take the bus to the nearest Disney hotel (whether or not your staying there... Doesn't matter) is sometimes the fastest way to get a bus to another park. But Disney Springs has transportation to all parks!! Or you can airways take the taxi that you may see bear the buses... Sometimes a lot less stressful depending on the number of tired children... Always worth looking into... Plus they know the quicker routes and side/service roads and well worth the $15 or so plus sometimes you get dropped off right at entrance... Depending on driver/park/reloading/etc.
Yes, however to go from park to park you sometimes have to make a transfer.
Yes! There are loads of buses to all the parks, the run all day long and the schedule for them all is at each park bus terminal. 🚌
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