The Monopoly Deal Rules for Deal Breaker cards section contains a list of Rules and frequently asked questions pertaining to how Deal Breaker cards can be used, when they can be used, and what they can do. The official Monopoly Rules are used to answer as many of the questions as possible. If the official rules are not known for that question then the generally accepted answer is used.
1. When I use the Deal Breaker card take take a full set that has a house or a house and hotel on it do I get the house and hotel with the full set?
Yes, a player using the Deal Breaker card for a completed property set gets everything that has been previously laid with that completed set. So if any houses or hotels have been laid on top of the completed property set that you are asking for, you would get the full property set including any houses/hotels when using the Deal Breaker card.
2. What happens if someone lays a Deal Breaker card on a player that doesn't have a full set?
A card laid is a card played. Since the player was not paying attention to the cards on the table, the Deal Breaker cards gets discarded into the discard pile and they do not get to take any properties. This move also counts as a card play during their turn.