I have no idea what the difference is between someone who is trustworthy and someone who is not. I try to be a good judge of character but it's embarassing when you trust some One and you find out you were wrong.
I'm asexual and I don't understand what it means when someone is "hot". Also, I was 13 before I knew not to put metallic things in the microwave and 15 before I could figure out the can opener. If it makes you feel better, I don't think there is an objective way to know if someone is trustworthy. You just have to constantly revise that opinion based on how you see them act.