the immobiliser won't forget its code, no matter how long its not had a battery, if it turns over, check you are getting a spark art the end of the lead, if so check you are getting fuel. just pull off the inlet pipe and switch ignition on and it will squirt out.
if not check the fuel cut off switch on the drivers side kick panel. if all the above are ok you should check if the injectors are working. you will need to make up a tool for doing this. a bulb with 2 wires poke the wires into the injector plug and get someone to turn the engine over. try these.