You cant, not really any ways. Objects or animals cant be stacked or on other objects or animals. it may appear that things are on top of things, but that's when there is a glitch in the game.
You cannot.
Most people "trap" the farmer by surrounding them with haybales or other items
you get yarn.
The black cat produces yam.
You get yarn from the cat, and 86 coins
Yarn
yarn
Same way you get everything else in FarmVille. A friend has to fine a lonely black cat on their farm, post it on their wall, then you have to click on it before all of your friends do.
If you have a cat, when it is 100%, you get the option to "brush kitten" (it's the kitten version of "harvest").
try chucking 80 lb haybales
you jump between them
you brush it and you get its fur.