If your cat is on advantage and goes outside all day and is inside only at night will your flea problem go away inside the house?
1) No it wont. So maybe try a flea collar that helped a lot for my cat.
2) No it really won't go away. you need to go to the vet and they sell a special spray that you need to spray around the house. follow the instructions coz it's quite potent and the hoover and clean thoroughly. this should stop the problem.
3) Advantage is to prevent fleas on the cats body. It is not intended to kill the fleas already in your house. They can survive by biting you, your other pets, even the mice in the walls. If the infestation it too great to be taken care of by the spray bottle, you'll need to buy flea bombs from the hardware store. Each bomb releases a cloud of pesticide, so be sure to follow the safety instructions on the package.