What happened to my VW 1.8t mk4 Bora (2005)?

She cranks (slowly) but won’t start. Died going uphill, started back up and died for good shortly after. Here’s the backstory :

There is a coolant leak somewhere, every week or so my gf would have to fill up the car with water to prevent it from overheating. I didn’t get a chance to thoroughly check where the source of the leak was, but it seemed to be coming from the front of the engine. I suggested that she buy some stop leak until I could pinpoint the source. So she went put bought the stopleak with the pellets and put it in.

A few days later, after I shut off the car, I noticed a gurgling sound coming from the coolant res. I pop the hood to find coolant spewing out from the cap. I replaced the cap and she took the car to work the next morning. According to her, while she was driving on the freeway she noticed a big loss of power and when she started up hill the car "just shut off". No shudder, jerk, or smoke. She then tried to start it but to no avail. A minute later she was able to start it again, but upon going uphill it again "shut off". This time there was smoke under the hood. She waited and tried to start it by that’s the last time it ever ran.

She says the temp gauge never showed it running hot, nor was the car gurgling like it had previously. When I checked the car, I found oil all over the place: under the hood, the valve cover, hoses, radiator…it seemed to have come out of the oil cap, as it was now loose but not open. The coolant was now like chocolate milk. I also found oil in my intake, turbo inlet and outlet, intercooler and air box. My spark plugs were dry and ok, and when I looked in to the cylinder from the spark plug hole i didn’t see any water or oil inside. My code reader only shows one code, P0864, which i guess is TCM communication problems. I did my Google’s and it seems my no start problem is related to this. Any suggestions would be a great help!