Adoption is usually used to establish a legally accepted parent-child or custodial relationship. If your sister-in-law is a minor without custodial parents, it might be possible to adopt her, but as your child, not as your sister. Consult an attorney familiar with adoption law in your area, petition the courts and see if it works.
Your sister in law is your husband's sister or your brother's wife.
Yes
Yes.
Probably your niece-in-law.
Yes in the US you can since you already have a bond with her.
Minors are not allowed to adopt.
i think it is
Yes, if the parents of the child (your sister and the father) allow it.
You're wife's brother's wife is your sister-in-law.
Of course if your sister let you!
No but his parents adopt Billy
Yes. You can marry your LIVE wife's sister if you want to, provided that you are both free to marry.