The child must be available for adoption...that means the parental rights of the birth parents must be terminated legally. I have one friend who signed over her rights to someone else so that an adoption could take place.
If both of your biological parents either agree to allow you to be adopted or have their parental rights terminated by the court. Also the friend would have to meet the standards set down in your...
Yes, in most states if she/he is an adult and consents to the adoption. Check the laws in your area for more information. Adult adoptions can be done pro se.