I tried starting it again and the engine refused to run?

My car has been fine since all the repairs to it were done. Today, I went out to get some items in the next town over which is further than normal when I go out for a drive. The drive there was nearly 11 miles.

On the way home I took a detour and did about 15-16 miles. Part of the journey was on the highway, and I went quite fast (up to 80 miles an hour, far more than I normally do) until the next junction.

When nearing home, I was stopped at a traffic light when I began to smell exhaust fumes. At the time I thought that the junction itself was polluted. When moving away from the lights the car was a little bit sluggish and did not accelerate as quickly. More gas needed to be given for the acceleration to be as good as before.

When I got home, I got out and saw that a lot of blue acrid smoke was coming out of the exhaust. It smelt and looked like carbon was being burnt off. I turned the engine off and took the stuff out of the car to deposit in the kitchen. This took about 5 minutes. When I came out to put the car in the garage, I had trouble getting the car to start (initially it wouldn't after a few seconds of turning the engine over) and had to give it gas the second time which I have normally never had to do (in the past it would start right up). I then parked it in the garage.

About 90 minutes later I had to go out again and when I tried starting it, it turned over for a second or so and then there was an awful crunch/grinding noise and it stopped completely (like what happened when I got hydraulic lock). When I tried starting it again the engine refused to turn over. I popped the hood and felt the engine and it was still very hot which surprised me. It also caused me some concern and I wondered if somehow the engine had seized.

I have no idea what has gone wrong.

There may be an issue that I failed to deal with.

In 2018, after I got the car working after replacing the car's computer, I had put in Amsoil, a bottle of Prolong and Auto RX, an oil based detergent that cleaned the engine of all the gunk accumulated over time. The recommended time to was to change the oil after 500 miles due to the amount of dirt that would come off of the metal of the engine components. I have not done that yet and I have done over 1,000 miles. I checked the oil and the oil was between the maximum and minimum on the dipstick. The oil didn't seem to be too dirty.

When looking in the engine compartment, I did not see any leaks.

Is there any way I can determine what has happened to the engine?