Hi, can anyone help me please?

I've had a few problems with my 95 WRX recently, last week the car would spin over but would not fire up! I called out the breakdown service who managed to get the car started by holding down the accelerator pedal, and told me they thought it was probably flooded!
They said if it happened again I should be able to get it started the same way! They did not have any explanation as to why it had flooded though.
It happened again 3 days later and managed to get it started eventually! Once started I took the car for a 20 min run, then stopped to get some petrol and the car would then fire up but was so badly misfiring that you could not even drive it!
So, got the car towed home again went to locked it up and the whole alarm system had shut down completely, including the immobiliser which no longer was working.
I had the alarm system reset, but as soon as you turned the iginition on it again it shuts the whole alarm system down again!

Does anyone have any ideas what might be causing these problems?
I'm not sure if the alarm problem is linked to the running problems or whether it's just a coincidence they've both gone wrong at the same time!!!

Any help would be greatly appreciated!

Thanks,
Carleen