1.Oil sensor warning light means you have low oil ( you should never let it get that low, check it regular basis as the 2.0 loves its oil). Fill it up with 5w-40 oil ASAP. This should turn your light off, its not warning you that somethingh is wrong, just telling you your low.
2.The key sounds werid likes it not turning off the alarm, but its a strange one because its only doing it with the boot and not the doors? Might need a trip to the local stealers to make sure the key is working properly.