The presence of fuel does not mean pressure. I understand you can borrow a fuel pressure gauge from some auto parts stores.took fuel line off up by motor and it was leaking fuel after I tried to crank. So I believe yes it was pumping gas. I had blew lines out the day before so they were dry.
For spark take out a spark plug ground it to the car. If you trust the spark plug wire you could hold it while someone tries to start the car. The spark should have a steady pattern. If you have, or can borrow a timing gun you can quickly check the high voltage coil wire and spark plug wires.
If you have fuel pressure check the injectors. people use a stick or long screw driver to touch a injector and their ear. You should hear the injector click. Again you could borrow a "noid light" that would plug in instead of a injector but this only proves the PCM is signalling the injector. Worst case some injectors may be stuck open or closed but in this case the engine would usually try to start or run badly.
The reason the forum focuses on spark and injectors first is that if they operate normally the OPTI is also functioning normally.
In most cases car alarms disable the starter circuit. This give the owner a obvious indication the car is disabled. IE: no starter.
Normally you would find a aftermarket relay cut into the yellow starter wire.
Standard alarm installs will have aftermarket relays to blink park lights and/or honk the horn. Other relays connecting to the ignition switch main power wires suggest a remote starter or a alarm disable. Or a lazy installer getting power from a "easy" place.
Like any motor you need air, fuel, and spark.