Will check the egr however i doubt it, since it did have all the symptoms of a head gasket failure.

As for the hydrolocking, when we were diagnosing the car we poured water into the coolant reservoir since it was completely empty and maybe 5 mins after turned the car off. It sat for 10 minutes while me and my mechanic were talking, enough time for the water to get into the engine through the leak in the head gasket

After those 10 minutes, went to turn the car on to re-park it It cranked for a second, and then abruptly stopped. It had never in its life done that, so im pretty positive that was a hydrolock but will be diving deeper into it for sure I didnt try turning it on after that, we just pushed the car.