Depends on where you live. Some allow from 18 and others not until you are 25. If you are related to the child that can also play a role.
No, to adopt a child you have to be at least 18 years old.
18
absolutly
Yes, you can adopt at any age above 18
8 weeks old
You can't adopt an adult. And his child is not an orphan, so you can't adopt him either. You can marry the man and then adopt his son.
Really You are never to old to adopt, or do anything.
You'll have to be 18.
No, most places require you to be at least 21 to be considered to adopt someone.
It is generally appropriate to adopt a kitten when they are around 8-12 weeks old.
Cleaveland steamer
it depends on how old it is.