The orbit of this launch was such that they could not come back to the launchpad like they did in December when they were successful in landing a first stage. They said in a few interviews that every failure is a learning experience that gives them more and more data. When the Falcon Heavy flies, the middle "first stage" will need to land on one of the barges if they want to return and reuse the segment.I've heard that they had to be very judicious with their trajectory adjustments for the first stage landing, since it was such a large payload/high orbit
I'm not certain. I do know that the fins at the top of the rocket are there due to lessons learned from the first failed attempt. They have also changed the way the landing legs work. The California landing attempt failed when one of the legs did not deploy correctly due to all the fog and moisture in the air turning to ice on the side of the rocket. I'd assume that each attempt helps them refine the flight control software and gives them more data on how much fuel they need for landing etc. I'm still amazed that they have hit that barge every attempt. Now they just need the rocket to stay upright at landing to pull this off.