Consider the following statements regarding Quantum Gravity:

1. It is a theoretical model that seeks to merge gravity, as explained by general relativity, with the principles of quantum mechanics that apply to particles at extremely small scales.

2. Quantum gravity helps explain phenomena such as what occurs inside black holes and the conditions that existed immediately after the Big Bang.

3. Einstein's general theory of relativity successfully integrated gravity with quantum principles, offering a complete explanation of quantum gravity.

How many of the above statements are correct?