It went boom. Pretty much zero visibility so not much to see. Seems like the worst of all the test launches. It blew up mid flight right as the landing burn initiated. Not sure what caused the RUD yet.

SN8 - SN11 were all more or less the exact same vehicle. SN15 will be the next to fly and it has a lot of upgrades so hopefully we see some progress when it flies.

What happened to 12,13,and 14?

Ok so ill try and summarize.

Spacex doesn't build one vehicle at a time. They're constantly building parts for multiple vehicles at the same time. I wouldn't be surprised if they're already building parts for SN20. Thats how they're able to have test launches in such short succession.

Every time they test a vehicle (whether its a flight test or just cryotesting), they learn a great deal and they try to implement that new knowledge into future designs. In this case, they learned enough from prior tests that sn12-14 were obsolete and weren't worth completing. I'm guessing sn11 was far enough along in the build process that it just made sense to finish it and launch it. I guess SN12-14 were early enough in their construction that it wasn't worth finishing them so they were just scrapped. That decision was made a while ago, I think they've already been demolished.

SN15 is supposed to have "hundreds of upgrades" according to Elon so hopefully we see some more progress when it launches. Hopefully that'll be in the first half of April.