You can tap the coin or star sign on the top right hand corner and download apps for free or pay for them
Buy them from the "store" on the app.
There are no easy FREE Stars yet, only if you install the promoted apps you can get a few free stars here and there. Having said that, talk is that there might be a "STAR TREE" in the making, maybe in the next update.
No, you cannot.
999999999
The only way to get stars is to either a) purchase star packs with real money or b) install and open free/paid apps listed and then open the app. The next time you play Tap Zoo, you will see the stars earned. Follow the link below for the latest offers. If you check your free star offers regularly, you can easily collect up to 400 FREE Tap Zoo stars. Although there is talk that a "Star-Tree" might become available in one of the next few updates. This tree should give you "free stars" at certain intervals. Don't expect any easy options though before at least version 1.9 is released.
You can't you have to purchase it
You collect them from your animals
get a rhino basically
Reach level 19 and you can buy it for 49 stars
Reach Level 17 and you can buy it for 489 stars
Reach Level 17 and you can buy it for 489 stars