Answer:
I am heavy forward, but backward I'm not. What am I?
There was a girl half my age when I was 12, now I am 66, how old is she?
The time between daylight and darkness when blood drinkers like to come out
I am a mini solar powered computer.
What has a head but never weeps a bed but never sleeps can run but never walks and banks but no money?
No matter how little or how much you use me, you change me every month.