18
leave from home
Not
Tell them to leave you alone.
The best way to get a stepsister to leave you alone is to ask her nicely. If she still doesn't leave you alone, you will need to speak to your parents.
You do drugs.
Just explain to them that you need a little space. If you do it calmly, they will most likely leave you alone till you are ready.
I have to disagree with the statement you made. Parents that have a gun in the house should have secure storage for it, and teach children to leave guns alone, and teach them gun safety.
13+
place a mirror in front of him
12
Adult children like...? 18 years old? Yes if you live in your parents house and you are 18 or older your parents can ask you to leave.