I find it interesting that not only is this rocket literally three Falcon 9s strapped together (including two that are reused) but they've not even taken the legs off. They don't look like they're going to unfold very well, though.
They haven't taken the legs off because they're going to attempt to land all 3 cores, probably 2 at the launch site and 1 on the drone ship
That's extra-impressive, then.
The three cores are boing to seperate from each other during the flight, and then are planned to individually land after the mission. The two outer cores are going to separate first, while the center core continues to propel the second stage a bit further up.
In case you are wondering about the fuel, the centre core throttles back as much as it can shortly after liftoff and then throttles up again after the two side boosters separate.