How does the Foster care placement system work? How do they pick a home for a child?
If you are in a safe location, it's unlikely you would be moved to another home. You can talk to your worker about your options, though. One option might be placement in a group home. An acquaintance of mine was removed from her mother's care at age 15, went to a few foster homes which didn't work out for various reasons, then was placed in a residential group home until she turned 18. Overall, unless conditions where you live are terrible, living in a home is more pleasant than a group home.
Most states / countries have foster care social workers whose job is to answer questions like yours. New Zealand is likely different than Australia, mate.
Stupid idea. You don't know how horrible some people are because in most cases, you get money for the child and you could be put with someone who is hungry for money and treat you like garbage. Listen, if you're in a good home right now and you're not being abused, then stay there. Foster care is not a good place at all. Too many kids come out abused, used, broken, and silenced.