Are all grass eating animals have 4 stomachs?

Giraffes belong to the clade Ruminantia. All members of this clade have a four chambered stomach. The first chamber is where chewed food ferments. Every so often, they belch up some of the partially digested plants, or cud, from the first stomach, and chew it again. The next two chambers act as a filter, allowing small particles to pass to the fourth chamber, but sending larger particles back to the first chamber. The fourth chamber uses enzymes to further work on digesting the food.