ECU fault codes (OPEL Vectra A 1994 engine 20NE)

I have really hard start, bad idling, and sometimes engine goes off gradually in about 5 seconds.
I’ve done the paper clip test with the 10 pin ALDL connector and the error codes are:

code 21 Throttle position sensor_high voltage

code 31 Engine RPM signal (crankshaft sensor)_No signal

code 73 Air flow sensor (AFS)_low voltage

I want to add that, I’ve checked the spark plugs and they’re wet of gas, also i looked inside of the cylinders and they are wet too.
I’ve attached a picture of one the spark plugs, they’re new spark plugs and they even didn’t work for 50 km, but that’s the condition of all of the spark plugs.
When i clean and dry them the engine starts without any pause, but mostly it doesn’t remain the same and it goes off after just 2-3 seconds or it goes to bad idling and then after some time the engine goes off.

Update: all of the fault codes went away after i changed the connectors and connections of the old wires, and the 31 code as @p1ns mentioned was just because i didn’t run the test with the engine running.
So i don’t have any fault codes now, but still abnormal volume of gas injected in the cylinders and i guess that’s the reason of hard start and bad idling. As i mentioned before, with dry spark plugs engine starts less than a second but it usually goes off after just 1-3 seconds and the spark plugs becomes completely wet of gas.

Any advice is really appreciated