In Northern Ireland, we would more naturally say 'this house is number nine" but that wasn't accepted
That would be "Цей будинок номер дев'ять".
Це can be this or it is.. Yeah.
Indeed. Did you try it?
Where is the article before the house (This is A house number nine.)?
What would that mean? As far as I know, when something is number something, we don't use articles "This is building number nine", "That's room number three"