Thank you all!! I was able to open the trunk using a screw driver. I just rotated the push button for couple of times and it opened. I dont have a key hole for the trunk instead there is a push button with a hole- weird eh I didnt realise this will bring me trouble while buying the car.
I tested the battery and it shows just 5.6 V. I checked the fuses in the engine compartment and the trunk everything looks fine except for cigarette lighter fuse.
I am not sure if I have to buy a new battery or charge this one and use it again. This was bought by the previous owner when I bought the car and I don't have a receipt for it. But I know it was new when I got the car. It was from Costco and it has 1000 CA and 850 CCA but no vent tube.
Any suggestions? Also will the cigarette lighter fuse cause battery drain?