ok i have a weird one - TL standard motor etc

I parked on an incline, nose up.

Alarm went off once. I stopped it with remote.

Goes off again about 15min later. I decide to move it to flatter ground.

WON'T start. Not even a click. Lights, windows, radio work fine. Error Code on Oddometer "S"

It won't jump start either. Road side assistance turned up, cannot jump start. Best it would do is a slight noise from motor, but no go. Battery tested and is fine. Says it's the starter motor.

Questions:

Could the alarm have gone off because of the incline? Could this have immobilised car? Or does it become mobilised once key is in?

Could the alarm have gone off due to lower voltage in battery?

Why did the alarm go off when there was a starter motor problem?

I had a similar thing with my KJ. Not sure what the cause was but the positive terminal was loose and the battery was 3 years old. There's also a bonnet alarm switch above the driver's side headlight that might be worth looking at.

The 'S' on the odometer is for sedan on the trip computer set up, so you lost battery power at some point.

Your bonnet alarm switch might be somewhere else on a TL.

Sounds like you have either a dead battery or improper connection on battery terminals.
I've had my alarm go off when battery was low too, everything you've said I experienced when my battery was going flat/dieing.

The S on the odometer shows you lost power, I'd bet on something in the electrical system isn't connected properly.

If you experienced a temporary short, like if the main starter terminal touched the body as it was loose, the instant drop in voltage would have set the alarm off and also reset the computer. So seeing as it happened on a incline, maybe the slope has been enough to cause something to short for an instant. I'd follow the path of the heavy cable to the starter as they would have to be prime suspects - if it was a thinner cable the fusible link would have blown.