Blown head gasket, likely cause????

I might add that the drivers side of the engine is referred to as the left side,as are any other direction specific parts on the car, and the pistons on that left side are numbered 1-3-5-and 7. While the cylinders on the passenger side, the right side,are numbered 2-4-6, and 8.So pic #4 is showing the left bank of cylinders; numbers 1-3-5 and 7.
If you knew all that and were simply referring to that last cylinder on the left side as the 4th from the front, and number 2 as being the 2nd from the front,well then,my apology.
Also, with that amount of detonation, if that was my engine, I would be inspecting the rod bearings too.And of course, backing down the timing and/or looking for better, more detonation-resistant fuel.