You have to reach Lv. 36 (you'll need to get a total of at least 97,000 exp).
Life force is the thing that helps you to not get lifeless zombies. You get it from decorations, and the more life force you have, the less of a chance there is to get lifeless zombies. However, the only way to never get lifeless zombies is to get the zombie monolith.
yes
Nothing
To get that farm banner on Zombie Farm, you've got to win an invasion and have some luck with the loot you get.
You cant. Thats in Plants vs. zombies, not zombie farm.
you cant .....
You buy it from the store.
shot it with an arrow
you get a zombutterfly
Combine flower zombie with flower zombie.
surround the zombie with plants