It sounds like the engine isn't seized anyway which is good, you're going to need to start pulling things apart though. I would get the exhaust downpipe off for a start, take off the boost pipes to the turbo too and feel the shaft of the turbo. It could be that the turbo has choked up the intake stopping the car from starting, maybe a busted impeller etc.
You could pop off the rocker cover too and have a little look at the cam for anything obvious, it should show signs of oil starvation if that's the problem.
If that's ok I'd probably try a compression test, that would certainly show wether the engine is fubarred.
Check the asv is wide open too, the thing on the side of the egr valve.
Not sure what else for now but that should keep you going for now lol.
You could pop off the rocker cover too and have a little look at the cam for anything obvious, it should show signs of oil starvation if that's the problem.
If that's ok I'd probably try a compression test, that would certainly show wether the engine is fubarred.
Check the asv is wide open too, the thing on the side of the egr valve.
Not sure what else for now but that should keep you going for now lol.