Zain, this is very patronising, but you are very young. It's good to see that you are thinking about things. No one has all the answers, but it doesn't mean you shouldn't ask the questions.

The world is full of omnivores and carnivores. Sure, the dinosaurs were too, but there is no evidence man killed them.

Wooly Mammoths and sabre toothed tigres on the other hand had intimate knowledge of man - we killed lots of one and were sometimes the dinner of the other. There are human bones with scars from sabre tooth tigers for example.

The earth covered with water. Where did it all come from? Where did it all go? And in 40 days remember!

A boat with the capacity for all that food??!?

Fossils are not dated by the depth that they are buried. The exact method depends, but the radioactive decay or carbon or the Argon / Potassium ratio is usually used. Fossils can be on the surface or miles underground. These values are not altered by much except time.

Crocodiles are not dinosaurs. They lived at the same time, but they are not the same. Different bone structure for example.