Answers to all your questions about dinosaurs from ChristianAnswers.net:
When did animals begin to kill and eat other animals?
Animal Hunter After the Flood, God gave people official permission to kill animals for food and eat them. Man could now eat everything, green plants and animals (Genesis 9:2,3). This means that people from Noah’s family could have eaten dinosaurs, if they tasted good.
But God told the animals (including dinosaurs) that they should not kill people. If they did, they would have to answer to God for it (Genesis 9:5b).
Tiger At the same time, the Bible does not say that animals were forbidden to kill other animals in this new world. God does not repeat his command, here or later, that animals are to eat plants. So, it could be that the end of the flood marks the time when land animals and birds began to develop the habit of killing for food. Or, it might just be the time when these habits started to become common.
Did any dinosaurs ever become terrible and ferocious?
The answer to this question remains a mystery. At this point, there is no proof that any of the dinosaurs were as mean and dangerous as shown in most dinosaur books. It will take many more discoveries before anyone can say for certain how dinosaurs behaved in the world before the Flood or after. However it is likely that more people killed dinosaurs than dinosaurs killed people.
Bible-believing Christians can be sure of one thing. When dinosaurs were originally created, they were peaceful and harmless just like all the other animals.