I, like you have no idea what is going on.
I don't know because I don't understand 100% what you are describing.
I get that the car won't start for you.
Terminology:
Cranking; the engine internals rotating due to the starter working causing the engine internals to rotate.
Starting the engine; turning the key to the start position to activate the starter.
So you have an engine that is not cranking when you try to start it. Best guess by me from your description. If you can't get the engine to crank over then you can't check for compression. If you can't get the engine to crank over then you can't get air into it. If you can't get the engine to crank over then you can't check for spark.
Now if the engine is cranking then you can check for the above. If it is cranking then you are saying that it will not stay running.
By now you are likely thinking that I am being some kind of F****** jerk. Not really trying to be but some times things like that come out.
Can you provide a more clear precise description of what the car is or isn't doing?
Thanks